Primary prevention

Vaccines

  • Vaccines are available under temporary emergency use or conditional marketing authorizations in various countries, including the UK, the US, Europe, Canada, China, and Russia.

    • Immunization programs generally prioritize people who are at highest risk from serious disease or death (e.g., residents and staff in care homes, older people, healthcare workers, and those with underlying health conditions). However, priorities differ between countries and you should consult local guidance.

    • It is unknown whether vaccines prevent asymptomatic infection or transmission from individuals who are infected despite vaccination. Vaccinated people should continue to follow public health recommendations. Safety and efficacy, including duration of immunity, beyond 2 months is unknown.[315][316] Advice will be updated as information on the impact of vaccination on virus transmission and indirect protection in the community is assessed.[317]

  • Surveillance of adverse events is extremely important, and may reveal additional, less frequent serious adverse events not detected in clinical trials.

    • For example, the Pandemrix® vaccine used during the 2009-2010 swine flu pandemic was withdrawn from the market due to an association with narcolepsy.[318] 

    • The new authorized mRNA vaccines have not been authorized for use in humans previously, so there is no long-term safety and efficacy data available for these types of vaccines.

    • All suspected adverse reactions should be reported via the Yellow Card scheme in the UK. Yellow Card: coronavirus (COVID-19) external link opens in a new window

    • All suspected adverse reactions should be reported via the Vaccine Adverse Event Reporting System (VAERS) in the US. Vaccine Adverse Event Reporting System external link opens in a new window

  • Vaccine dose schedules may differ across locations.

    • There have been suggestions about extending the length of time between doses, reducing the number of doses, changing the dose (half-dose), or mixing and matching different COVID-19 vaccines in order to vaccinate more people. However, there is no evidence to support these strategies.[319]

    • The World Health Organization (WHO) recommends that countries experiencing exceptional epidemiologic circumstances may consider delaying the administration of the second dose for a short period (up to 42 days based on currently available clinical trial data) as a pragmatic approach to maximizing the number of individuals benefiting from a first dose while vaccine supply continues to increase. Countries should ensure that any such program adjustments to dose intervals do not affect the likelihood of receiving the second dose.[317]

    • In the UK, the Joint Committee on Vaccination and Immunisation recommends that delivery of the first dose to as many eligible individuals as possible should be initially prioritized over delivery of a second dose.[320][321] However, there is a lack of evidence to support an extended dose interval between the first and second dose, and this is outside of the manufacturer's authorized dose recommendations.[322]

    • In the US, the Food and Drug Administration recommends following authorized dosing schedules.[323]

    • Consult local guidelines before administering vaccines. Patients must give free and voluntary informed consent prior to vaccination.[324]

  • The table below compares the two vaccines that have been authorized for use in the US.

    • In addition to these, AstraZeneca COVID-19 vaccine (a chimpanzee adenovirus vector vaccine that carries the severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] spike protein) has been authorized in the UK, CoronaVac® and Sinopharm® (inactivated version of the SARS-CoV-2 virus) have been authorized in China, and Sputnik V® (an adenovirus vector vaccine) has been authorized in Russia.

    • Several other vaccine candidates are still in development including mRNA vaccines, DNA vaccines, viral vector vaccines, protein subunit vaccines, live-attenuated vaccines, inactivated virus vaccines, and intranasal delivery systems.[325]

    • WHO: draft landscape of COVID-19 candidate vaccines external link opens in a new window

com.bmj.content.model.Caption@1c8691a1[Figure caption and citation for the preceding image starts]: Comparison of selected authorized COVID-19 vaccines. Data is evolving; consult local drug formulary or guidelines for detailed information for your location. *See Vaccine efficacy data and Vaccine safety data sections below for detailed information. **Dose schedules may differ in some locations. Last updated: 13 January 2021 BMJ Best Practice editorial team; compiled using data from the UK product information [Citation ends].

Vaccines and anaphylaxis or vasovagal reactions

  • Severe allergic reactions, including anaphylaxis, have been reported outside of clinical trials in the general population after vaccination with mRNA vaccines. Monitoring by the VAERS in the US detected 21 cases of anaphylaxis after administration of a reported 1,893,360 first doses of the Pfizer/BioNTech vaccine (11.1 cases per million doses) as of 23 December 2020; 71% of these reactions occurred within 15 minutes of vaccination.[326] It has been suggested that these reactions may be due to the presence of lipid pegylated ethylene glycol (PEG), or PEG derivatives such as polysorbates.[327]

    • The WHO recommends that a history of severe allergic reaction (e.g., anaphylaxis) to any component of the vaccine is a contraindication to vaccination, and people with an immediate allergic reaction to the first dose should not receive additional doses. A history of any immediate allergic reaction to any other vaccine or injectable therapy is considered a precaution, but not a contraindication, to vaccination. Perform a risk assessment to determine the type and severity of reaction and the reliability of the information. These people may still be vaccinated, but the risks should be weighed against the benefits of vaccination, and the recipient should be observed for 30 minutes after vaccination in healthcare settings where anaphylaxis can be treated immediately. Anaphylactic reactions have also been reported in people without a history of severe allergic reactions. Administer vaccines only in settings where anaphylaxis can be treated, and observe for at least 15 minutes after vaccination. Food, contact, or seasonal allergies are not considered a precaution. There is no contraindication or precaution to vaccination for people with latex, egg, or gelatin allergies.[317]

    • The UK-based Medicines and Healthcare products Regulatory Agency recommends that anyone with a previous history of allergic reactions to the ingredients of the vaccine should not receive it, but those with any other allergies such as a food allergy can have the vaccine.[328]

    • Vaccination should only be carried out in facilities where resuscitation measures are available, and a protocol for the management of anaphylaxis must be available. Recipients should be monitored for at least 15 minutes after vaccination. A second dose should not be administered to anyone who experienced anaphylaxis after the first dose.[329]

    • Guidelines on vaccinating people with a history of allergy or anaphylaxis may differ across locations; consult local guidance.

  • Anxiety-related reactions, including vasovagal reactions and hyperventilation, may occur. Ensure precautions are in place to avoid injury from fainting.

Vaccines and specific patient populations

  • There are limited or no data available from clinical trials about the use of vaccines in specific patient populations. Despite this, the WHO recommends that the following populations may be vaccinated:[317]

    • Older people (without an upper age limit)

    • People with comorbidities that have been identified as increasing the risk for severe disease

    • Immunocompromised people who are part of a group recommended for vaccination

    • People living with HIV who are part of a group recommended for vaccination

    • People with autoimmune conditions who have no contraindications to vaccination

    • People with a history of Bell palsy who have no contraindications to vaccination 

    • People with a history of symptomatic or asymptomatic SARS-CoV-2 infection.

  • Delayed vaccination is recommended in people with an acute febrile illness or current acute COVID-19, and in people who previously received passive antibody therapy for COVID-19. Delayed vaccination may be considered in people who have had confirmed SARS-CoV-2 infection in the preceding 6 months (until near the end of this period). 

  • The Norwegian Medicines Agency recommends conducting more thorough evaluations of very frail older patients before vaccination, after 23 patients died shortly after receiving the Pfizer/BioNTech vaccine. However, it is currently unknown whether there is a connection between these deaths and the vaccine. The agency has investigated 13 of the deaths so far and has concluded that common adverse reactions of mRNA vaccines, such as fever, nausea, and diarrhea, may have contributed to fatal outcomes in some of the frail patients.[330][331]

Vaccines and pregnant/breastfeeding women

  • Use caution in pregnant and breastfeeding women as there are no safety and efficacy data available.

    • The WHO recommends not using vaccines in pregnant women, unless the benefits outweigh the potential risks (e.g., healthcare workers at high risk of exposure, women with comorbidities that place them in a high-risk group for severe disease). It recommends that women who are breastfeeding, and who are part of a group recommended for vaccination, should be offered vaccination on an equivalent basis. It does not recommend discontinuing breastfeeding after vaccination.[317]

    • Public Health England recommends that pregnant women should not routinely be vaccinated; however, vaccination may be considered when the potential benefits outweigh the potential risks for the mother and fetus.[332] It recommends that women who are breastfeeding can receive the vaccine.[333]

    • The American College of Obstetricians and Gynecologists recommends that COVID-19 vaccines should not be withheld from pregnant or breastfeeding women who meet criteria for vaccination based on recommended priority groups. Discuss the risks and benefits with the person before vaccination. Pregnant and breastfeeding women who decline vaccination should be supported in their decision.[334]

Vaccine efficacy data

  • Pfizer/BioNTech COVID-19 vaccine

    • Efficacy is based on an interim analysis of results from a phase 3 trial of 43,448 participants (with randomization to vaccine and placebo arms in a 1:1 ratio). The vaccine is reported to be 95% effective in preventing symptomatic COVID-19 after 2 doses compared with placebo (saline), in people ages 16 years and older. This is based on an analysis of 170 confirmed cases of COVID-19 with an onset at least 7 days after the second dose among recipients with no evidence of existing or prior SARS-CoV-2 infection (8 cases in the vaccine arm versus 162 cases in the placebo arm). Efficacy was 52% after the first dose. Among 10 cases of severe disease with onset after the first dose, 9 cases occurred in the placebo arm and 1 case occurred in the vaccine arm. This only provides preliminary evidence of vaccine-mediated protection against severe disease.[315] A small preprint study suggests the vaccine may be effective against new variants with spike protein mutations.[335] However, more data are required.

  • Moderna COVID-19 vaccine

    • Efficacy is based on an interim analysis of results from a phase 3 trial of 30,420 participants (with randomization to vaccine and placebo arms in a 1:1 ratio). The vaccine is reported to be 94.1% effective in preventing symptomatic COVID-19 after 2 doses compared with placebo (saline) in people ages 18 years and older. This is based on an analysis of 196 confirmed cases of COVID-19 with an onset at least 14 days after the second dose among recipients with no evidence of existing or prior SARS-CoV-2 infection (11 cases in the vaccine arm versus 185 cases in the placebo arm). Among 30 cases of severe disease (including one fatality) with onset after the first dose, all cases occurred in the placebo arm and none in the vaccine arm.[336]

  • AstraZeneca COVID-19 vaccine

    • Efficacy is based on an interim analysis of pooled data from four ongoing randomized controlled clinical trials with 11,636 participants conducted in the UK, Brazil, and South Africa. The vaccine is reported to be 70.4% effective in preventing symptomatic COVID-19 after 2 doses compared with control (meningococcal vaccine or saline) in people ages 18 years and older. This is based on an analysis of 131 confirmed cases of COVID-19 with an onset at least 15 days after the second dose among recipients with no evidence of existing or prior SARS-CoV-2 infection (30 cases in the vaccine arm versus 101 cases in the placebo arm). Trial results are yet to be published. Efficacy and safety data are currently limited in people ≥65 years of age.[337]

Vaccine safety data

  • Pfizer/BioNTech COVID-19 vaccine

    • Safety is based on an interim analysis of results from a phase 3 trial of 43,448 participants. The reactogenicity subset included 8183 participants.[315]

    • Local adverse reactions were more common in the vaccine group compared with placebo, with the most common reaction being injection-site pain within 7 days after injection (83% after the first dose and 78% after the second dose in younger participants; 71% after the first dose and 66% after the second dose in older participants). Less than 1% of participants reported severe pain. Local adverse reactions were similar after the first and second doses.

    • Systemic adverse reactions were more common in the vaccine group compared with placebo, and were reported more often by younger patients and after the second dose. The most commonly reported systemic adverse reactions after the second dose were fatigue (59% in younger participants; 51% in older participants), headache (52% in younger participants; 39% in older participants), and fever (16% in younger participants; 11% in older participants). Severe systemic events were reported in <2% of participants after either dose, except for fatigue and headache after the second dose.

    • Other rare adverse events included lymphadenopathy, shoulder injury (related to vaccine administration), paroxysmal ventricular arrhythmia, and right leg paresthesia.

  • Moderna COVID-19 vaccine

    • Safety is based on an interim analysis of results from a phase 3 trial of 30,420 participants.[336]

    • Solicited local and systemic adverse reactions were reported in 87.8% of participants within 7 days after the first dose in the vaccine group compared with 48% in the placebo group, and 92.2% of participants within 7 days after the second dose in the vaccine group compared with 42.8% in the placebo group. The most commonly reported solicited adverse reactions included injection-site reactions, fatigue, headache, myalgia, and arthralgia. These reactions were more commonly reported and were more severe after the second dose. Solicited adverse reactions were more common among participants ages 18 to 64 years compared with adults ages ≥65 years. 

    • Unsolicited adverse events related to vaccination (up to 28 days after any injection) were reported in 8.2% of participants in the vaccine group compared with 4.5% in the placebo group. The incidence of severe adverse events was higher in the vaccine group compared with the placebo group (0.5% versus 0.2%). The most commonly reported unsolicited adverse events (reported in at least 1% of participants) were fatigue and headache. The relative incidence of these events was not affected by age.

    • Bell palsy occurred more commonly in the vaccine group (three cases) compared with the placebo group (one case), suggesting that it may be more than a chance event. This will require close monitoring as larger populations are vaccinated outside of clinical trials.

  • AstraZeneca COVID-19 vaccine

    • Safety is based on an interim analysis of pooled data from four ongoing randomized controlled clinical trials with 23,745 participants conducted in the UK, Brazil, and South Africa (trial results are yet to be published).[338]

    • The most frequently reported adverse events were: injection-site reactions (>60%); headache, fatigue (>50%); myalgia, malaise (>40%); fever, chills (>30%); arthralgia, nausea (>20%). Adverse reactions were milder and reported less frequently after the second dose and in adults ages ≥65 years.

Vaccine trial limitations

  • A key limitation of the data is the short duration of safety and efficacy follow-up. Trials were not sufficiently powered to detect less common adverse events reliably, and the median follow-up time was only 2 months after the second dose. Trials do not address whether the vaccine prevents transmission or affects infectiousness, and the duration of protection is yet to be determined. There are no data on children or younger adolescents, pregnant or breastfeeding women, or immunocompromised people. There are also no data to assess efficacy in populations at high risk of severe disease, in people previously infected with SARS-CoV-2, against long-term effects of disease, or against mortality.[315][336]

  • There are concerns that the trials were not designed to detect a reduction in any serious outcome such as hospital admissions, use of intensive care, or deaths, or whether the vaccines can interrupt transmission of the virus – two key primary end points in vaccine efficacy trials.[339] Also, since the trials have been published, important questions about final efficacy data exclusions, as well as concerns about the use of pain and fever medications, unblinding, and primary event adjudication committees have been raised.[340]

  • Planned long-term follow-up of participants is unlikely to occur in the context of trials due to the ethics of following a placebo recipient long-term without offering the vaccine. This could inadvertently threaten ongoing vaccine research that is yet to define immunologic correlates of protection against COVID-19, which could vary according to the vaccine platform, individual characteristics, age groups, and population subset.[341][342][343]

  • Previous trials of coronavirus vaccines identified cellular immunopathology and antibody-dependent enhancement (ADE) as potential safety issues. There are concerns over ADE of SARS-CoV-2 due to subsequent exposure to wild-type SARS-CoV-2 post vaccination and prior exposure to other coronaviruses (such as those that cause the common cold).[344][345] Available data do not indicate a risk of vaccine-enhanced disease with the mRNA vaccines; however, data are limited and the risk over time, potentially associated with waning immunity, remains unknown and needs to be evaluated further.[315][336]

Infection prevention and control for healthcare professionals

  • Always consult local infection prevention and control protocols; only basic principles are detailed here.

  • Immediately isolate all suspected or confirmed cases in an area that is separate from other patients. Place patients in adequately ventilated single rooms if possible. When single rooms are not available, place all cases together in the same room and ensure there is at least 3 feet (1 meter) between patients.[346]

  • Implement standard precautions at all times:[346]

    • Practice hand and respiratory hygiene

    • Give patients a medical mask to wear

    • Wear appropriate personal protective equipment

    • Practice safe waste management and environmental cleaning.

  • Implement additional contact and droplet precautions before entering a room where cases are admitted:[346]

    • Wear a medical mask, gloves, an appropriate gown, and eye/facial protection (e.g., goggles or a face shield)

    • Use single-use or disposable equipment. 

  • Implement airborne precautions when performing aerosol-generating procedures, including placing patients in a negative pressure room.[346]

    • Some countries and organizations recommend airborne precautions for any situation involving the care of a COVID-19 patient.

  • All specimens collected for laboratory investigations should be regarded as potentially infectious.[346]

  • Appropriate personal protective equipment gives healthcare workers a high level of protection against COVID-19. A cross-sectional study of 420 healthcare workers deployed to Wuhan with appropriate personal protective equipment tested negative for SARS-CoV-2 on molecular and serologic testing when they returned home, despite all participants having direct contact with COVID-19 patients and performing at least one aerosol-generating procedure.[347] Standard surgical masks are as effective as respirator masks for preventing infection of healthcare workers in outbreaks of viral respiratory illnesses such as influenza, but it is unknown whether this applies to COVID-19.[348] 

  • Detailed infection prevention and control guidance is available:

Telehealth for primary care physicians

General prevention measures for the general public

  • People should be advised to:[350][351]

    • Wash hands often with soap and water for at least 20 seconds or an alcohol-based hand sanitizer (that contains at least 60% alcohol), especially after being in a public place, blowing their nose, or coughing/sneezing. Avoid touching the eyes, nose, and mouth with unwashed hands

    • Avoid close contact with people (i.e., maintain a distance of at least 3 feet [1 meter]) including shaking hands, particularly those who are sick, have a fever, or are coughing or sneezing. Avoid going to crowded and poorly ventilated places. It is important to note that recommended distances differ between countries (for example, 6 feet [2 meters] is recommended in the US and UK) and you should consult local guidance. However, there is no evidence to support a distance of 6 feet (2 meters)[352]

    • Practice respiratory hygiene (i.e., cover mouth and nose when coughing or sneezing, discard tissue immediately in a closed bin, and wash hands)

    • Seek medical care early if they have a fever, cough, and difficulty breathing, and share their previous travel and contact history (travelers or suspected/confirmed cases) with their healthcare provider

    • Stay at home and self-isolate if they are sick, even with mild symptoms, until they recover (except to get medical care)

    • Clean and disinfect frequently touched surfaces daily (e.g., light switches, door knobs, countertops, handles, phones).

Face masks in community settings

  • Recommendations on the use of face masks in community settings vary between countries.[353] It is mandatory to wear a mask in public in certain countries or in certain situations, and masks may be worn in some countries according to local cultural habits. Consult local public health guidance for more information. 

  • There is no high-quality or direct scientific evidence to support the widespread use of masks by healthy people in the community setting, and there are risks and benefits that must be considered. Data on effectiveness is based on limited and inconsistent observational and epidemiologic studies.[89] The first randomized controlled trial to investigate the efficacy of masks in the community (in addition to other public health measures such as social distancing) found that the recommendation to wear surgical masks when outside the home among others did not reduce incident SARS-CoV-2 infection compared with no mask recommendation. However, the study did not assess whether masks could decrease disease transmission from mask wearers to others.[354] A Cochrane review found that wearing a mask may make little to no difference in how many people caught influenza-like illnesses; however, this is based on low-certainty evidence, and does not include results of studies from the current COVID-19 pandemic.[355] Evidence for mask effectiveness for respiratory tract infection prevention is stronger in healthcare settings compared with community settings; direct evidence on comparative effectiveness in SARS-CoV-2 infection is insufficient.[356][357] Randomized trials have not addressed the question of source control.

  • Despite the lack of good-quality evidence, the WHO advises that in areas of known or suspected community or cluster transmission, people should wear a nonmedical mask in the following circumstances: indoor or outdoor settings where physical distancing cannot be maintained; indoor settings with inadequate ventilation, regardless of whether physical distancing can be maintained; and in situations when physical distancing cannot be maintained and the person has a higher risk of severe complications (e.g., older age, underlying condition). Caregivers and those living with suspected or confirmed cases should wear a medical mask when in the same room, regardless of whether the case has symptoms. Children ages up to 5 years should not wear masks for source control. A risk-based approach is recommended for children ages 6 to 11 years. Special considerations are required for immunocompromised children, or children with certain diseases, developmental disorders, or disabilities. The WHO advises that people should not wear masks during vigorous-intensity physical activity. Use of a mask alone is insufficient to provide adequate protection, and they should be used in conjunction with other infection prevention and control measures such as frequent hand hygiene and social distancing.[89]

  • Potential harms and disadvantages of wearing masks include: potential increased risk of self-contamination due to manipulation of face mask and touching face/eyes, or when nonmedical masks are not changed when wet or soiled; headache and/or breathing difficulties; facial skin lesions, irritant dermatitis, or worsening acne; discomfort; difficulty communicating; social and psychological acceptance; false sense of security; poor compliance; waste management issues; and difficulties for patients with chronic respiratory conditions or breathing problems.[89] Masks may also create a humid habitat where the virus can remain active and this may increase viral load in the respiratory tract; deeper breathing caused by wearing a mask may push the virus deeper into the lungs.[358] 

  • Cloth masks have limited efficacy in preventing viral transmission compared with medical-grade masks.[359] Efficacy depends on the type of material used, the number of layers, the degree of moisture in the mask, and the fitting of the mask on the face. In a study comparing the use of cloth masks to surgical masks in healthcare workers, the rates of all infection outcomes were highest in the cloth mask arm, with the rate of influenza-like illness statistically significantly higher in this group. Moisture retention, reuse of cloth masks, and poor filtration may result in increased risk of infection.[360] 

Alcohol-based hand sanitizers

  • The Centers for Disease Control and Prevention has issued a warning about alcohol-based sanitizers containing methanol (which may be labeled as containing ethanol). Methanol poisoning should be considered in patients who present with relevant signs and symptoms (e.g., headache, impaired vision, nausea/vomiting, abdominal pain, loss of coordination, decreased level of consciousness) who report ingestion of hand sanitizer or frequent repeated topical use. Cases of permanent blindness and death have been reported.[361]

  • Frequent use of hand sanitizers may result in antimicrobial resistance. Accidental ingestion, especially by children, has been reported.[362]

Travel-related control measures

  • Many countries have implemented travel-related control measures including complete closure of borders, partial travel restrictions, entry or exit screening, and/or quarantine of travelers. Overall, low to very low evidence suggests that travel-related control measures may help to limit the spread of infection across national borders. Cross-border travel restrictions are likely to be more effective than entry and exit screening, and screening is likely to be more effective in combination with other measures (e.g., quarantine, observation).[363]

  • Entry/exit screening: people traveling from areas with a high risk of infection may be screened using questionnaires about their travel, contact with ill persons, symptoms of infection, and/or measurement of their temperature. Low-certainty evidence suggests that screening at travel hubs may slightly slow the importation of infected cases; however, the evidence base comes from two mathematical model studies and is limited by their assumptions. Evidence suggests that one-time screening in apparently healthy people may miss between 40% and 100% of people who are infected, although the certainty of this ranges from very low to moderate. In very low‐prevalence settings, screening for symptoms or temperature may result in few false negatives and many true negatives, despite low overall accuracy. Repeated screenings may result in more cases being identified eventually and reduced harm from false reassurance.[364] Entry screening at three major US airports found a low yield of laboratory-diagnosed cases (one case per 85,000 travelers) between January and September 2020.[365]

  • Quarantine: enforced quarantine is being used to isolate easily identifiable cohorts of people at potential risk of recent exposure. Despite limited evidence, a Cochrane review found quarantine to be important in reducing the number of people infected and deaths, especially when started earlier and when used in combination with other prevention and control measures. However, the current evidence is limited because most studies are based on mathematical modeling studies that make assumptions on important model parameters.[366] The psychosocial effects of enforced quarantine may have long-lasting repercussions.[367][368]

  • Travelers who arrive in the UK are required to self-isolate for 10 days unless they have traveled from an exempt country. Public Health England: coronavirus (COVID-19) – how to self-isolate when you travel to the UK external link opens in a new window

Social distancing

  • Many countries have implemented mandatory social distancing measures in order to reduce and delay transmission (e.g., city lockdowns, stay-at-home orders, curfews, nonessential business closures, bans on gatherings, school and university closures, travel restrictions and bans, remote working, quarantine of exposed people). 

  • Although the evidence for social distancing for COVID-19 is limited, it is emerging, and the best available evidence appears to support social distancing measures to reduce the transmission and delay spread. The timing and duration of these measures appears to be critical.[369][370] When comparing countries with more restrictive nonpharmaceutical interventions (e.g., mandatory stay-at-home and business closure orders) to countries with less restrictive nonpharmaceutical interventions, implementing any nonpharmaceutical interventions was associated with a significant reduction in case growth. However, there was no clear, significant beneficial effect of more restrictive nonpharmaceutical interventions compared with less restrictive nonpharmaceutical interventions in any of the countries studied. It should be noted that the study has important limitations.[371]

  • Researchers in Singapore found that social distancing measures (isolation of infected individuals and family quarantine, school closures, and workplace distancing) significantly decreased the number of infections in simulation models.[372]

  • Harms must also be considered. Public health policies mostly rely on models and these models often ignore potential harms including excess death and inequalities arising from economic damage, negative health effects, and effects on vulnerable populations.[373] Negative consequences of community-based mass quarantine include psychological distress, food insecurity, economic challenges, diminished healthcare access, heightened communication inequalities, alternative delivery of education, and gender-based violence.[374]

Shielding extremely vulnerable people

  • Shielding is a measure used to protect vulnerable people (including children) who are at very high risk of severe illness from COVID-19 because they have an underlying health condition. Shielding involves minimizing all interactions between those who are extremely vulnerable and other people to protect them from coming into contact with the virus. 

  • Extremely vulnerable groups include:[375]

    • Solid organ transplant recipients

    • People with specific cancers

    • People with severe respiratory conditions (e.g., cystic fibrosis, severe asthma, or severe COPD)

    • People with rare diseases that significantly increase the risk of infections (e.g., homozygous sickle cell disease, severe combined immunodeficiency) 

    • People on immunosuppression therapies sufficient to significantly increase the risk of infection

    • People with spleen problems (e.g., prior splenectomy)

    • Adults with Down syndrome

    • Adults on dialysis or with chronic kidney disease

    • Women who are pregnant with significant heart disease (congenital or acquired)

    • Other people who have also been classed as clinically extremely vulnerable based on clinical judgment and an assessment of their needs.  

  • The UK government recommends that clinically extremely vulnerable people are urged to follow specific precautions based on current public health restrictions:

  • Consult current guidance for specific recommendations (recommendations may differ between countries).

  • Shielding advice for children and young adults is available. Consult current guidance for specific recommendations (recommendations may differ between countries).

Lifestyle modifications

  • Lifestyle modifications (e.g., smoking cessation, weight loss) may help to reduce the risk of COVID-19, and may be a useful adjunct to other interventions.[376]

  • The WHO recommends that tobacco users stop using tobacco given the well-established harms associated with tobacco use and second-hand smoke exposure.[235] Public Health England also recommends stopping smoking. Public Health England: COVID-19 – advice for smokers and vapers external link opens in a new window

Pre-exposure or postexposure prophylaxis

  • There are no drugs recommended for pre-exposure prophylaxis or postexposure prophylaxis, except in the context of a clinical trial.[3] See the Emerging section for more information.

Immunity passports

  • Some governments are discussing or implementing certifications for people who have contracted and recovered from COVID-19 based on antibody tests (sometimes called "immunity passports"). Possession of a passport would allow people to have a greater range of privileges (e.g., work, education, travel). However, the WHO does not support these certifications as there is currently no evidence that people who have recovered from infection and have antibodies are protected from reinfection.[377] Other potential issues include lack of public support for these measures, potential for discrimination of groups of people, testing errors (including cross-reactivity with other human coronaviruses), access to testing, fraud, legal and ethical objections, and people getting infected intentionally in order to obtain a certification.[378]

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