J&J Booster vaccine has strong response

LONDON — Johnson & Johnson said Tuesday that a booster of its one-shot coronavirus vaccine provides a stronger immune response months after people receive a first dose.

J&J said in statement that an extra dose — given either two months or six months after the initial shot — revved up protection. The results haven’t yet been published or vetted by other scientists.

The J&J vaccine was considered an important tool in fighting the pandemic because it requires only one shot. But even as rollout began in the U.S. and elsewhere, the company already was running a global test of whether a twodose course might be more effective — the second dose given 56 days after the first.

That two-dose approach was 75 percent effective globally at preventing moderate to severe COVID-19, and 95 percent effective in the U.S. alone, the company reported — a difference likely due to which variants were circulating in different countries during the monthslong study.

Examined a different way, the company said when people got a second J&J shot two months after the first, levels of virus-fighting antibodies rose four to six times higher. But giving a booster dose six months after the first J&J shot yielded a 12-fold increase.

While the single-dose vaccine remains strongly effective, “a booster shot further increases protection against COVID19 and is expected to extend the duration of protection significantly,” Dr. Paul Stoffels, J&J’s chief scientific officer, said in a statement.