The Delta variant is wreaking havoc throughout the country: Cases are rising in nearly every state, breakthrough infections are being reported more and more, and some areas have already reinforced mask mandates. But while health experts, including the Centers for Disease Control and Prevention (CDC), maintain that our vaccines are effective against the Delta variant, new research has already shown that its spread is reducing efficacy—like in one recent study showing that Johnson & Johnson is significantly less effective at preventing symptomatic infection with the variant. Now, new research has found that the Pfizer vaccine will only work against the Delta variant if you do one thing.
Researchers from the U.K. sought to determine how effective COVID vaccines are against the Delta variant in a new study, published July 21 in The New England Journal of Medicine. The study analyzed more than 19,000 teens and adults across the U.K., with researchers estimating the proportion of cases caused by the Delta variant or Alpha variant through sequencing and comparing them to the patients’ vaccination status.
According to the study, the Pfizer vaccine is less effective against the Delta variant if people have not gotten their second dose. The researchers found that one shot of Pfizer is only 36 percent effective against symptomatic disease when confronted with this variant. “Effectiveness after one dose of vaccine was notably lower among persons with the Delta variant,” the study confirms.
The Pfizer vaccine was significantly more effective for fully vaccinated individuals. With two doses, the vaccine is about 88 percent effective against symptomatic disease from the Delta variant, according to the study.
“It’s clear how important the second dose is to secure the strongest possible protection against COVID-19 and its variants,” Matt Hancock, the U.K.’s health and social care secretary, who was not involved in the study, said when an unreviewed preprint of the study was released in May.
In the U.S., the CDC is urging people to get their second doses. “The Pfizer and Moderna vaccines are most effective, especially when—against the Delta variant—given as two shots in a series,” CDC director Rochelle Walensky
said during a July 16 White House press briefing. “Not completing the series put those partially vaccinated at risk of illness.”
The CDC says that you should get your second shot of the Pfizer vaccine three weeks after the first, or at least as close to this interval as possible. If you’ve already gone longer than this, the agency is now saying you should get the second dose no matter how much time has passed.
“We encourage that people get vaccinated on schedule three or four weeks after your first dose. But if you are beyond that window, I want to reiterate: There is no bad time to get your second shot,” Walensky said during the briefing.