Israeli officials say Pfizer vaccine less effective against Delta variant

Israeli officials Thursday announced a 30% decrease in the effectiveness of the Pfizer COVID-19 vaccine to prevent infection and mild to moderate cases.

The country’s Ministry of Health data shows high levels of circulating Delta variant and a relaxation of public health measures in early June led to a drop in the Pfizer vaccine’s  prevention of “breakthrough” cases from 94% to 64% in recent weeks.

Still, it is important to consider the findings in context, experts say.

Israeli health officials are weighing the necessity of a third or booster dose of the Pfizer vaccine. Whether they will reinstate public health measures to prevent spread of COVID-19 also remains unknown.

Going forward, Israel intends to study if factors such as age, pre-existing conditions or time since immunization increases the risk of breakthrough cases.

According to the U.S CDC based on evidence from clinical trials in people 16 years and older, the Pfizer vaccine was 95% effective at preventing laboratory-confirmed infection with the virus that causes COVID-19 in people who received two doses and had no evidence of being previously infected.