Herd immunity is when enough people have protection that makes it unlikely a virus or bacteria can spread and cause disease. This protection can be either from a previous infection or vaccination. As a result, on average, the whole population within the community is protected. But those who are not protected because they have never had the disease, didn’t get vaccinated or the vaccine didn’t protect them could still get sick. This is why it is not a good idea to rely on herd immunity to protect yourself instead of getting vaccinated.
The percentage of people who need to have protection to reach herd immunity varies by disease.
Some estimates for COVID-19 suggest it may be near 60 to 70%. However, herd immunity calculations may not be reliable in the context of COVID-19 because of many unknowns. The effectiveness of COVID-19 vaccines in preventing asymptomatic infection remains unknown right now. For this reason, herd immunity calculations will only give an estimated target for vaccination programs.
Until the effects of the COVID-19 vaccines have been fully studied, it is best to not assume that vaccinations will protect others. We must continue to protect ourselves and others by:
- wearing a mask
- physical distancing
- practicing hand hygiene
- staying home and getting tested when sick
These measures will help to continue to stop the spread of COVID-19.