COVID-19 vaccines may not prevent spread of virus, so mask-wearing, other protections still critical

Jake Ellison

Excitement and relief over news of vaccines that help prevent people from getting sick, winding up in the hospital or dying from COVID-19, the disease caused by the coronavirus, are warranted, says University of Washington’s Dr. Larry Corey. But, these messenger RNA (mRNA) vaccines may not prevent people from getting infected or spreading the virus.

COVID-19 vaccines may not prevent spread of virus, so mask-wearing, other protections still critical

Larry Corey

Answering questions around how vaccines affect transmission of the virus is “of obvious importance” and research will be conducted once people begin getting vaccinated, Corey writes in a new COVID-19 Vaccine Matters blog jointly produced by Johns Hopkins University and the UW. But we all must still wear masks, physically distance, wash our hands frequently, and avoid large gatherings — even when most people have been vaccinated.

“If vaccinated individuals are capable of transmitting infection,” Corey writes, “then anybody who is not vaccinated fares no differently before than after the introduction of a COVID-19 vaccine. With vaccine hesitancy resulting in fewer people agreeing to be vaccinated, we do not yet know whether and when we will be able to markedly reduce the public health implications of COVID-19 and reduce its circulation in the workplace, in close communities and stop super-spreading events.”

In addition, Corey notes that mathematical models suggest that vaccines could create a situation in which many more people carry the virus without showing symptoms, become more cavalier about whether they can spread the virus and therefore unknowingly infect even more people.

“This realization helps explain why we must optimize coverage and overcome vaccine hesitancy, especially in persons who are at high risk,” Corey writes.

To read this and other articles by Corey and other experts, visit the COVID-19 Vaccine Matters blog series created by Johns Hopkins and the University of Washington as an outcome of the joint symposium — Preserving the Scientific Integrity of Getting to COVID-19 Vaccines: From Clinical Trials to Public Allocation — the two universities hosted in October.

Dr. Larry Corey is an internationally renowned expert in virology, immunology and vaccine development and a leader of the COVID-19 Prevention Network (CoVPN), which was formed by the National Institute of Allergy and Infectious Diseases at the U.S. National Institutes of Health to respond to the global pandemic. He is a professor of medicine and virology at UW School of Medicine and a professor in the Vaccine and Infectious Disease Division and past president and director of Fred Hutchinson Cancer Research Center.


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