Researchers are rapidly trying to discern how well existing COVID-19 vaccines work against the delta variant of the coronavirus, which now accounts for 93 percent of COVID-19 cases in the U.S.
Six updates:
- Johnson & Johnson's COVID-19 vaccine was up to 71 percent effective against hospitalization from infection with the delta variant of the coronavirus in a South African study consisting of nearly 480,000 healthcare workers.
- In a separate study posted on the preprint server bioRxiv, researchers found Johnson & Johnson's COVID-19 vaccine may be much less effective against the delta and lambda variants of the virus compared to the original strain. They found that Johnson & Johnson's COVID-19 shot was significantly less effective at producing neutralizing antibodies against the variants. That study consisted of just 17 people vaccinated with two doses of an mRNA vaccine and 10 people vaccinated with one dose of Johnson & Johnson's shot.
- Two doses of Pfizer's COVID-19 vaccine were 88 percent effective against symptomatic disease from the delta variant of the coronavirus in a clinical trial conducted by Public Health England. It also found that AstraZeneca's vaccine was 67 percent effective against the delta variant. Both shots were far less effective after only one dose, about 30 percent effective.
- A third dose of Pfizer's COVID-19 shot "strongly boosts" the body's immune response against the delta variant of the coronavirus, the drugmaker said. In slides Pfizer posted ahead of an earnings call, the drugmaker showed data that antibody levels against the delta variant were five times higher in people ages 18 to 55 after a third dose and 11 times higher in 65- to 85-year-olds.
- Fully vaccinated people are 50 percent to 60 percent less likely to become infected with the delta variant of the coronavirus compared to unvaccinated people, according to a study conducted by Imperial College London in England.
- Moderna's COVID-19 vaccine demonstrated 93 percent efficacy for six months after the second dose, but the drugmaker said booster shots will most likely become necessary before winter to combat the rapid spread of the delta variant.