Can Covid-19 Vaccine Prevent Infecting Others? Scientists To Search For Answer


By Tara Copp & Michael Wilner

One of the Army’s chief scientists developing a COVID-19 vaccine often gets a question that is being asked by Americans across the country: Once a person is vaccinated, is it safe to visit parents and friends, or could they still infect them?

“Unfortunately, we haven’t answered that question yet,” said Dr. Kayvon Modjarrad, director of Emerging Infectious Diseases at the Walter Reed Army Institute of Research. “And so we have to operate on the assumption that you still have the ability to still have the virus and transmit, not get the disease, but be sort of a carrier.”

As more Americans are vaccinated, scientists will need to follow up with a study that conducts regular nasal swabs to determine if the COVID-19 virus can still attach to a vaccinated person, resulting in a positive test, even if it doesn’t make them sick, he said.

Democratic Reps. Brad Schneider, D-Ill., Pramila Jayapal, D-Wash., and Bonnie Watson Coleman, D-N.J., who sheltered with unmasked Republican colleagues during the U.S. Capitol riot reported they all tested positive in the days after the violent attack.

Each had received their initial dose of the COVID-19 vaccine before they tested positive, according to media reports.

“Following the events of Wednesday, including sheltering with several colleagues who refused to wear masks, I decided to take a Covid test. I have tested positive,” Coleman tweeted this week.

The scientific community is unclear whether individuals testing positive after receiving their first dose of vaccine were infected before or after the shot. The incubation period for COVID-19 — the period between infection and the onset of symptoms — can be as short as two days, or as long as two weeks, Modjarrad noted.

“It is a big open question as to whether or not these vaccines, even after two doses, prevent infection, or do they just prevent disease?” Modjarrad said. “Because the primary endpoint in these clinical trials for the two authorized vaccines were disease, not asymptomatic infection.”

For now, Modjarrad cautions everyone to continue wearing a mask and taking social distancing precautions, in order to protect those who have not been vaccinated.

Initial vaccine goals at Walter Reed and by pharmaceutical companies developing vaccine candidates “were trying to prevent disease and death here first and foremost,” Modjarrad said. “But we would like to get to a vaccine that prevents transmission as well. And they may, we just don’t know yet.”

Modjarrad’s own family is anxious for those answers as well.

“It can be frustrating, I know, for a lot of people, including my family members and friends who ask me the same questions. And we’re trying to go as quickly as possible,” Modjarrad said. “Until we have those questions answered, we still have to take an abundance of caution.”


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    • Editor-in Chief:
    • Theodore Massey
    • Editor:
    • Robert Sokonow
    • Editorial Staff:
    • Musaba Dekau
      Lin Takahashi
      Thomas Levine
      Cynthia Casteneda Avina
      Ronald Harvinger
      Lisa Andonis

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