Question: Once you are vaccinated, can you still get infected with the SARS-CoV-2 virus? My understanding from watching the FDA proceedings on Moderna and Pfizer vaccines is that vaccinated individuals are protected from severe consequences (illnesses and sickness) resulting from SARS-CoV2, but they can still get the virus (and transmit to others) once they are immune. So while a vaccinated person is largely protected from getting sick, they can still be infected with the virus after being vaccinated. My mother, who is a critical care pulmonologist, said her understanding was that a vaccinated person would no longer acquire SARS-CoV2. It’s a nuance that’s come up quite a bit in my conversations with family over the past week, and I’ve found little data on this particular issue.
Answer: The short answer is that we just don’t know yet. The Pfizer and Moderna clinical trials had primary endpoints of symptomatic infection (e.g. sickness), but the data have been insufficient to assess asymptomatic infection. Basically, a vaccinated person has a good deal of protection from becoming sick with COVID, but we don’t know whether they have protection from becoming infected and contagious. This is why it’s so important that vaccinated individuals continue to follow public health protocols, including mask wearing and social distancing. Our Q&A of 1/11 discusses this issue in more detail.
Since then, a bit more potentially good news has surfaced. Israel’s Clalit Institute released its preliminary (not yet peer reviewed) analysis of infections following vaccination. Researchers compared the rate of laboratory confirmed test positives between individuals ages 60+ who received the first Pfizer dose and those who were unvaccinated. Researchers found that “14 days after the injection of the first vaccine, there is a real decrease in the rate of infection.” If these study findings hold, it could mean that vaccination provides some protection against asymptomatic infection too. More research is underway to answer this important question!