FACT BRIEF

Are scientists working to understand the impact of COVID-19 vaccines on transmission of the coronavirus?

Thursday, May 6, 2021

By Jacob Alabab-Moser

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YES

COVID-19 vaccines protect individuals from contracting the disease, but scientists continue to look for stronger evidence that they can impede transmission of the coronavirus that causes the disease.

The data so far suggests at least some benefit. An Israeli study found that vaccinated people carry a lower “load” of the virus, suggesting a potential for reduced transmission. A U.S. study, awaiting peer review, found that household members of vaccinated health care workers were at lower infection risk than household members of unvaccinated workers.

Results from another modeling study suggest that the initial vaccines may not fully prevent transmission by vaccinated individuals, particularly when the vaccinations begin late in an ongoing outbreak. In addition, uncertainties remain around the roles of asymptomatic carriers, as well as seasonal effects on immunity.

This fact brief is responsive to conversations such as this one.

Sources

Centers for Disease Control and Prevention Science brief: Background rationale and evidence for public health recommendations for fully vaccinated people

Science News Moderna and Pfizer COVID-19 vaccines may block infection as well as disease

Nature Initial report of decreased SARS-CoV-2 viral load after inoculation with the BNT162b2 vaccine

medRxiv Effect of vaccination on transmission of COVID-19: a preprint of a observational study in healthcare workers and their households

The Lancet Analysis of the potential impact of durability, timing, and transmission blocking of COVID-19 vaccine on morbidity and mortality

John Hopkins University Coronavirus Resource Center: Vaccines FAQ

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