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UW researcher: CDC's mask announcement does not undermine COVID-19 vaccine effectiveness

The vaccine is effective against protecting those vaccinated from severe illness but new science has raised concern over who can spread the delta variant.

SEATTLE — After hearing the Center for Disease Control’s new guidelines recommending vaccinated people return to wearing mask indoors, Washington Congressmember Cathy McMorris Rodgers reacted in a statement saying, "The CDC's updated guidance deeply undermines vaccine confidence. Mask mandates for more command and control will not build trust-only resentment".

Dr. Ali Mokdad at the University of Washington’s Institute for Health Metrics and Evaluations said the CDC’s announcement should not undermine confidence in the vaccine.

“The vaccines are highly effective. It's very important to remind everybody, the vaccines are highly effective,” Mokdad said.

Projections from the IHME show universal masking will save lives. In Washington state, projections say 800 to 1,300 lives can be saved by November 1, if everyone begins wearing a mask.

The delta variant, which is now the prominent variant in the United States, is what's fueling changes to the CDC’s mask guidelines. The CDC reports there’s new science that suggest vaccinated people should wear a mask to prevent the spread of the delta variant.  

“In rare occasions, some vaccinated people infected with the delta variant after vaccination may be contagious and spread the virus to others,” CDC Director Dr. Rochelle P. Walensky said.

The vaccines are designed to protect individuals from severe illness and all COVID-19 vaccines approved in the United States are effective against the delta variant. A study printed in the New England Journal of Medicine found the Pfizer vaccine is 88% effective at preventing illness for those fully vaccinated.

This new discovery, however, means while the vaccine will protect the vaccinated from getting severely ill, if someone vaccinated contracts the delta variant they may still give it to someone else.

“There is a sense that I’m vaccinated so I’m immune, which is true, you will be asymptomatic once you are infected, but you are spreading the virus. That’s why it's very important to wear a mask,” Mokdad said.

The new data about those vaccinated spreading the delta variant emerged over the last couple of days. The data is unpublish and the CDC has not released it. It involves more than 100 samples from several states and one other country.

“It is concerning enough that we feel like we have to act,” Walensky said.

The American Society for Microbiology estimates Delta is "40 to 60 percent more transmissible than the Alpha variant and almost twice as transmissible as the original Wuhan strain of SARS-CoV-2."

Dr. Mokdad expects cases to get worse this winter. He says what we're seeing now is a preview of what's to come.

"The fact that we’re seeing [a rise in cases] right now is a danger sign. It tells us that this delta variant is a stubborn virus, is more likely to be transmitted and we need to put up our guards and we need to be very careful,” Mokdad said.