Maintain diligence after vaccination

Dear Dr. Roach: Could you please provide your recommendations on how we should conduct ourselves after we get the COVID vaccine? Please include an explanation of how immune we actually will be.

T.S.

Answer: Three vaccines are approved under an emergency authorization at the time of this writing: Two mRNA vaccines, made by Moderna and Pfizer, and the Johnson & Johnson vaccine, which uses a different virus and DNA to “teach” our cells how to respond to COVID-19.

The available mRNA vaccines are both nearly 95% effective at preventing disease after two doses; the single-dose Johnson & Johnson vaccine was 66% effective in preventing moderate to severe COVID-19 but 100% effective at preventing COVID-19-related hospitalization and death. This is very good protection, but given how prevalent the infection is throughout North America, exposure to the virus is very likely unless you take proper precautions. This includes maskwearing and hand-washing, but also avoiding high-risk exposures, such as eating indoors or being in a large group of unmasked people. Even those who had the vaccine can still get COVID: 66% and 95% are good, but not perfect. Also, that high protection takes time — two to three weeks after the full series.

A second issue is that we just aren’t sure whether the vaccine keeps people from being contagious. It may be that even people protected from COVID-19 illness may still be infectious for a time after they get exposed. Recent data suggest the vaccines are very effective at doing so but the data is not yet conclusive.

For these two reasons — protecting yourself from COVID-19 (imperfect vaccines) and protecting others (unknown protection against possible asymptomatic spread) — experts recommend continuing to take precautions. As more and more people get the vaccine, the pandemic will subside.

As the prevalence decreases, life will return to normal, and masks and social distancing can be stopped. How soon that will be depends on how fast the population can be vaccinated, and how careful people are about masks and social distancing until then.