Transmission after COVID-19 mRNA vaccination: Infectious disease expert available for interviews

The approved mRNA vaccines are critical tools to move past the pandemic. However, as of February 2021 questions persist around whether getting vaccinated can prevent someone from spreading the disease to others, requiring us to hold on to our masks a bit longer.

After your COVID-19 vaccine

When you are immunized with one of the COVID-19 mRNA vaccines, the first dose prompts your immune system to generate many different antibodies and immune memory and the second dose prompts the immune system to refine its antibodies and results in improved immune memory. It typically takes about two weeks after the second dose to obtain the vaccine’s full effect.

Getting both doses provides protection from the worst of the virus, but it doesn't offer a return to pre-pandemic behaviors just yet.

“Getting vaccinated is highly protective,” said Richard Martinello, MD, Infection Prevention, Yale New Haven Health, “However, while the virus remains circulating to a high degree, public health measures such as masking and social distancing still need to be followed. We expect as more people get vaccinated we will see a decrease of COVID-19 on a population level and public health guidelines will be updated.”

Post-vaccination transmission

Public health officials are collecting data to understand the degree to which vaccinated people can pass the virus on to unvaccinated people.

Moderna is conducting research to determine if the vaccine provides neutralizing antibodies that stop the virus from replicating and therefore prevent someone from being infectious, or in other words, being an unknowing carrier. A trial of 52 people showed that vaccinated participants were much less likely to have COVID-19 viral particles identified in their nasal swabs than unvaccinated participants.

“These results hint at neutralizing antibodies, but this was a small study and more data is needed,” said Dr. Martinello. “We think if virus is present in someone’s nose they are likely contagious, but we don’t really know the presence and amount of virus associated with the spread of the disease.”

The factors that differentiate a highly contagious person with COVID-19 verses someone who doesn’t spread the disease continues to be studied.

“These transmission questions are causing us to think deeper about how respiratory viruses spread in general,” said Dr. Martinello. “Research efforts behind these questions can help guide better clinical and public health decisions. In the meantime, these highly effective vaccines mark significant progress in the fight against COVID-19.”