A single injection of the BioNTech / Pfizer vaccine produces a robust antibody response in weeks, according to Israeli data that can help inform whether scarce global supplies can be increased by delaying second doses.
At the Rambam Health Care Campus in northern Israel, 91 percent of the 1,800 doctors and nurses who received the two-dose vaccine showed a large presence of antibodies 21 days after the first injection, before receiving the second dose, according to Michael Halberthal , chief executive of the hospital. Another 2 percent showed a moderate presence of antibodies.
“If 93 percent had an important response three weeks after the first injection, that raises a good question, that you may prefer to use the first injection on more people,” said Dr. Halberthal.
At Sheba Medical Center, similar serological tests at different intervals showed at least 50 percent of the team with an antibody level “above the cutoff” two weeks after the first injection, said Arnon Afek, associate director-general of the network. hospitals.
Data from the two hospitals are based on individual antibody responses to the vaccine and do not provide a definitive assessment of the effectiveness of a single injection. BioNTech / Pfizer clinical trials were based on two injections, 21 days apart, and did not measure the antibody response. Pfizer said it could not comment on independent studies.
However, it is likely that the first findings will encourage scientists who have argued that the time between the first and second doses of Covid vaccines could be extended to stretch limited supplies.
“This goes for what is up for grabs in the UK now, if you continue to give just a first dose, so people get certain levels of immunity, or go to the second,” said Afek
Israel has enough vaccine supplies and is not expected to change its strategy. He plans to inoculate the entire adult population in mid-March. “The question of whether the first shot is sufficient will not be answered by Israel,” said Afek. “Our policy is to give two chances, but the data we collect is significant.”
Israel’s rapid vaccination program is being closely watched by epidemiologists looking for data on the vaccine’s effectiveness in the real world and the impact of vaccine-induced immunity on infection rates. The country of 9 million has already administered the first injections to more than a quarter of the population, the highest vaccination rate in the world. It has already administered the second injection to some 850,000 people, including 80% of the population over 60 years of age.
Frontline health workers were among the first to be vaccinated in Israel, providing a large sample of a population at risk since the end of December.
Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine, said the UK, which chose to space the first and second doses of the BioNTech / Pfizer injection beyond the recommended 21 days, is conducting its own studies.
“The UK will soon have its own data showing effectiveness after the first dose for the different vaccines currently in use and any policy changes should await more robust data,” he said.