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Vaccine May Be Weaker Than Previously Thought Against Delta, Risk Remains Highest In Unvaccinated

Photo courtesy Food and Drug Administration
Two dose vaccines were estimated to be 88% effective, but that number may be lower according to data released Monday

A new statement from the Israeli government released Monday says the Pfizer vaccine is 64% effective against the Delta variant of COVID-19. 


This is a new number and lower than earlier estimates. 


Dr. Dale Bratzler, University of Oklahoma’s chief COVID officer, says he previously quoted a study out of the United Kingdom that put vaccine effectiveness at 88%, but the Israeli data may be more reliable because Israel has a good testing program. 


“In Israel, they’ve identified more people who had a positive test but were asymptomatic. The vaccine is not as effective at preventing the spread of disease when you look at asymptomatic cases,” said Bratzler.


The vaccines will still lessen disease in vaccinated people. 


“I always tell people: think about influenza vaccines. We know that influenza vaccines in a typical flu year may be 50% or 60% effective at preventing the flu. But people who are vaccinated are very unlikely to end up in the hospital or in the critical care unit on a ventilator,” said Bratzler.


There is at least one significant factor that may slow the spread in unvaccinated communities that still isn't understood.


“There is a big unknown, and that’s people who have previously had COVID-19, how much protection did they get from natural immunity? We don’t know that very well yet. Unvaccinated people are clearly at the greatest risk from the Delta variant,” said Bratzler.


Analyzing data from the Centers for Disease Control, the Associated Press has reported that nearly all COVID deaths are among the unvaccinated.


Poorer counties have lower rates of vaccination.


According to the Oklahoma State Department of Health, as of July 6th, the average 7-day case count in Oklahoma is 278.