Israel’s nationwide campaign to provide its population with COVID-19 vaccine boosters appears to benefit recipients. A third dose of the Pfizer-BioNTech vaccine significantly lowers the risk of infection, according to two new studies.
A report for the country’s Ministry of Health, posted Friday, showed a third dose reduced recipients’ risk of testing positive for SARS-CoV-2 by more than 10-fold 2 weeks later. And in a preprint posted yesterday, researchers used data from a health maintenance organization (HMO) to calculate that a third dose roughly halves a person’s chances of testing positive for the virus starting 1 week after the shot and further reduces it after the second week.
Israel’s case numbers and hospitalizations continue to climb as the Delta variant spreads. The country recorded 10,947 new cases on Monday, more than on any other day since the start of the pandemic. But the number of cases in older people began to slow in the weeks after 31 July, when third doses of the messenger RNA vaccine were offered to people ages 60 and older—a sign that boosters may be working. On 29 August, Israel announced it would expand the booster program to everyone over the age of 12 whose second dose was at least 5 months earlier. More than 2.1 million people have already received a third dose, the government said yesterday.
Researchers from Israel’s Ministry of Health and several universities analyzed information about more than 1.1 million Israelis over the age of 60 in the ministry’s database, correlating COVID-19 diagnoses between 30 July and 22 August with whether and when people had received a booster. Twelve days after people received a third dose, they found, the risk of infection was reduced more than 10-fold. That brings protection back up to the 95% range seen shortly after the second dose. The effect against severe disease was even larger, reducing the risk 15 times, but the authors caution that small numbers of patients with severe disease and the study’s short time frame mean the result has a large uncertainty.