A fourth dose of a Covid-19 vaccine increases antibodies in the blood fivefold after one week, the Israeli prime minister said, referring to a preliminary study the day after the country began conducting the samples.
Israel on Monday began offering a fourth dose of the BioNTech / Pfizer vaccine to Israelis over the age of 60 and medical workers amid rising numbers of cases due to the Omicron coronavirus variant.
Prime Minister Naftali Bennett said the findings of the study, by Israeli researchers, were promising.
“Firstly, the fourth dose is safe. “This is a safety parameter similar to what we saw after the third dose – that’s good news,” Bennet said on Tuesday at Sheba Medical Center where the study was conducted.
“A week after we took the fourth dose, we saw a significant increase in the number of antibodies, a fivefold increase within one week,” he said. “This is an indication of a very high probability that the fourth dose will protect… Against infection to some extent and against severe symptoms.”
The study was conducted on 154 people from Sheba Medical Center who showed low antibodies and who received the third “booster” sting of the Pfizer vaccine before August 20th. Other preliminary studies from Israel have suggested that vaccine efficacy decreases after three to four months.
The European Medicines Agency announced late last year that it was reviewing whether fourth doses were needed for a subset of at-risk populations, such as those who are immunosuppressed. Immunocompromised people in the UK can have a fourth dose.
British health officials have said they are reviewing the available evidence as to whether it should be extended to the general population.
Israel was the first country in the world to deploy a third shot last July, a move credited with stopping the previous Delta variant wave. The fourth shot is now offered to those who both meet the criteria and received the third shot more than four months ago.
The government and health authorities said the main purpose of the fourth jab deployment is to protect the most vulnerable people from serious illness and death, avoid the collapse of the health system and keep the economy open.
As of Monday, the first day it was offered, about 100,000 qualifying Israelis had either received the vaccine shot or had already made appointments to do so.
More than 10,000 new Covid cases were reported in Israel on Monday, the highest daily figure since September and a 10-fold increase from mid-December. The number of seriously ill people increased at a much more gradual pace and stood at 117 on Tuesday, of which 92, according to data from the Ministry of Health, were not considered fully vaccinated.
While studies show that repeated boost infection occurs, emerging evidence suggests that dual vaccination, without boosters, can still protect against serious diseases, even when caused by Omicron.
A Harvard University study found this week cellular immunity remained durable against the variant. The finding is one of many pieces of evidence that will help global health authorities decide whether Omicron-targeted vaccines will be needed.
Additional post by Oliver Barnes in London