$复星医药(SH600196)$ According to a large new U.S. study results published in the Lancet, Pfizer (NYSE:PFE) - BioNTech's (NASDAQ:BNTX) coronavirus vaccine is 90% effective at preventing hospitalization for up to six months and 73% effective against COVID-19 infection.In the new study, the researchers analyzed the electronic health records from more than 3.4M members of Kaiser Permanente Southern California, between Dec. 14, 2020, and Aug. 8, 2021.Vaccine effectiveness against hospital admissions for infections with Delta variant for all ages was high overall (93% [95% CI 84–96]) up to 6 months.However, effectiveness declined from 88% during the first month after full vaccination to 47% after 5 months.Vaccine effectiveness against Delta variant also declined to 53% after four months from 93% after the first month of shot. Against other variants, efficacy waned to 67% at 4–5 months from 97%.Overall efficacy against Delta variant for the fully vaccinated was 75%, while for other variants was 91%.On the other hand, a recent study from the CDC reported that the vaccine’s effectiveness against hospitalization dropped to 77% after four months, compared to 91% in the first few months, The New York Times reports.Earlier, data from Israel indicates that the Pfizer vaccine’s efficacy dropped to 39% in late June and early July, down from 95% in January through early April.The findings could give fuel to both sides of the booster debate, said Sara Tartof, an epidemiologist at Kaiser Permanente Southern California and the first author of the study.Other COVID-19 vaccine makers: Moderna (NASDAQ:MRNA), Johnson & Johnson (NYSE:JNJ); AstraZeneca (NASDAQ:AZN); Novavax (NASDAQ:NVAX).