Prevention

Strategies for preventing transmission of the disease include social distancing, wearing of masks, washing hands, avoiding touching the eyes, nose, or mouth with unwashed hands, and coughing or sneezing into a tissue, and putting the tissue directly into a waste container.

Social distancing

Social distancing (also known as physical distancing) includes infection control actions intended to slow the spread of the disease by minimising close contact between individuals. Methods include quarantines; travel restrictions; and the closing of schools, workplaces, stadiums, theatres, or shopping centres. Individuals may apply social distancing methods by staying at home, limiting travel, avoiding crowded areas, using no-contact greetings, and physically distancing themselves from others. Many governments are now mandating or recommending social distancing in regions affected by the outbreak. Non-cooperation with distancing measures in some areas has contributed to the further spread of the pandemic.

The maximum gathering size recommended by U.S. government bodies and health organisations was swiftly reduced from 250 people (if there were no known COVID-19 spread in a region) to 50 people, and later to 10. On 22 March 2020, Germany banned public gatherings of more than two people. A Cochrane review found that early quarantine with other public health measures are effective in limiting the pandemic, but the best manner of adopting and relaxing policies are uncertain, as local conditions vary.

Older adults and those with underlying medical conditions such as diabetes, heart disease, respiratory disease, hypertension, and compromised immune systems face increased risk of serious illness and complications and have been advised by the CDC to stay home as much as possible in areas of community outbreak.

In late March 2020, the WHO and other health bodies began to replace the use of the term "social distancing" with "physical distancing", to clarify that the aim is to reduce physical contact while maintaining social connections, either virtually or at a distance. The use of the term "social distancing" had led to implications that people should engage in complete social isolation, rather than encouraging them to stay in contact through alternative means. Some authorities have issued sexual health guidelines for the pandemic, which include recommendations to have sex only with someone you live with, and who does not have the virus or symptoms of the virus.

Face masks and respiratory hygiene

The WHO and US CDC recommend individuals wear non-medical face coverings in public settings where there is an increased risk of transmission and where social distancing measures are difficult to maintain. This recommendation is meant to reduce the spread of the disease by asymptomatic and pre-symtomatic individuals and is complementary to established preventive measures such as social distancing. Face coverings limit the volume and travel distance of expiratory droplets dispersed when talking, breathing, and coughing. Face coverings also filter out viral particles from inhaled air, reducing the chance that the wearer will become infected. Many countries and local jurisdictions encourage or mandate the use of face masks or cloth face coverings by members of the public to limit the spread of the virus.

Masks are also strongly recommended for those who may have been infected and those taking care of someone who may have the disease. When not wearing a mask, the CDC recommends covering the mouth and nose with a tissue when coughing or sneezing and recommends using the inside of the elbow if no tissue is available. Proper hand hygiene after any cough or sneeze is encouraged. Healthcare professionals interacting directly with COVID-19 patients are advised to use respirators at least as protective as NIOSH-certified N95 or equivalent, in addition to other personal protective equipment.

Self-isolation

Self-isolation at home has been recommended for those diagnosed with COVID-19 and those who suspect they have been infected. Health agencies have issued detailed instructions for proper self-isolation.

Many governments have mandated or recommended self-quarantine for entire populations. The strongest self-quarantine instructions have been issued to those in high-risk groups. Those who may have been exposed to someone with COVID-19 and those who have recently travelled to a country or region with the widespread transmission have been advised to self-quarantine for 14 days from the time of last possible exposure.

Healthy diet and lifestyle

The Harvard T.H. Chan School of Public Health recommends that COVID-19 has made the maintenance of one's immune system more important than ever. Therefore, eating a healthy diet, being physically active, managing psychological stress, and getting enough sleep are critical. Dark-skinned people are at particular risk of a vitamin D deficiency which can impair the immune system.

Ventilation and air filtration

The WHO recommend ventilation and air filtration in public spaces to help clear out infectious aerosols.

Hand washing

Hand hygiene is extremely important to prevent the spread of SARS-CoV-2. The US CDC recommends that people wash hands often with soap and water for at least twenty seconds, especially after going to the toilet or when hands are visibly dirty; before eating; and after blowing one's nose, coughing, or sneezing. This is because, outside the human body, the virus is killed by household soap, which bursts its protective bubble. In addition, soap and water disrupts the sticky bond between pathogens and human skin which causes the coronavirus pathogen to slide off the hands/body. CDC has recommended using an alcohol-based hand sanitiser with at least 60 percent alcohol by volume when soap and water are not readily available. The WHO advises people to avoid touching the eyes, nose, or mouth with unwashed hands. It is not clear whether washing hands with ash, if soap is not available, is effective at reducing the spread of viral infections.

Surface cleaning

Surfaces may be decontaminated with a number of solutions (within one minute of exposure to the disinfectant for a stainless steel surface), including 62–71 percent ethanol, 50–100 percent isopropanol, 0.1 percent sodium hypochlorite, 0.5 percent hydrogen peroxide, and 0.2–7.5 percent povidone-iodine. Other solutions, such as benzalkonium chloride and chlorhexidine gluconate, are less effective. Ultraviolet germicidal irradiation may also be used. The CDC recommends that if a COVID-19 case is suspected or confirmed at a facility such as an office or day care, all areas such as offices, bathrooms, common areas, shared electronic equipment like tablets, touch screens, keyboards, remote controls, and ATM machines used by the ill persons should be disinfected.

Vaccine

On 4 February 2020, US Secretary of Health and Human Services Alex Azar published a notice of declaration under the Public Readiness and Emergency Preparedness Act for medical countermeasures against COVID‑19, covering "any vaccine, used to treat, diagnose, cure, prevent, or mitigate COVID‑19, or the transmission of SARS-CoV-2 or a virus mutating therefrom", and stating that the declaration precludes "liability claims alleging negligence by a manufacturer in creating a vaccine, or negligence by a health care provider in prescribing the wrong dose, absent willful misconduct". The declaration is effective in the United States through 1 October 2024.

On 9 November, Pfizer Inc announced that its vaccine was more than 90% effective in preventing COVID-19, and on 16 November, Moderna revealed its vaccine was 94.5% effective.