Can people who are fully vaccinated still transmit the virus to other people?
People are considered fully vaccinated if it’s been at least two weeks following the second dose of Pfizer-BioNTech or Moderna and at least two weeks after the single-dose Johnson & Johnson vaccine. COVID-19 vaccines do not always prevent infection. Fully vaccinated people can become infected asymptomatically or with minimal symptoms and can still spread COVID-19 to others. However, a growing body of evidence indicates that people fully vaccinated with an mRNA vaccine (Pfizer-BioNTech and Moderna) are less likely to have asymptomatic infection or to transmit COVID-19 to others. And the vaccines keep people from developing severe illness and ending up in the hospital.
There have been several real-world studies, in the U.S, Israel and the UK, that really show a profound reduction in asymptomatic infection, particularly with the mRNA vaccines. Similarly in a CDC study conducted in California and Texas, fully vaccinated healthcare workers were 25 times less likely to test positive for COVID-19 than those who were unvaccinated. Data from different studies in different countries suggest that people vaccinated with Pfizer-BioNTech who develop COVID-19 have a lower viral load than unvaccinated people. This observation may indicate reduced transmissibility, as viral load has been identified as a key driver of transmission.
Two other studies from the United Kingdom found significantly reduced likelihood of transmission to household contacts from people infected with COVID-19 who were previously vaccinated. In the Moderna trial, among people who had received the first dose, the number of asymptomatic people who tested positive for COVID-19 at their second-dose appointment was approximately two-thirds lower among those who are vaccinated than among placebo recipients (0.1% and 0.3% respectively). We do not have as much data yet with the Johnson & Johnson vaccine, but it does look to significantly reduce transmission. Further studies are underway to learn more about the benefits of Johnson & Johnson vaccine.
The risk of COVID-19 infection in fully vaccinated people cannot be completely eliminated as long as there is continued community transmission of the virus.
Tilahun Gemtessa, MD
MidState Medical Center