COVID-19 Booster Doses Boost Defenses, But How Long Will Protection Last

Israel’s national campaign to provide its population with COVID-19 vaccine boosters appears to be benefiting beneficiaries. A third dose of the Pfizer-BioNTech vaccine greatly reduces the risk of infection, according to two new studies.

Israel announced on August 29 that it was expanding the application of the third dose to the entire vaccine-eligible population, which in the country affects people over 12 years of age. The measure had been launched gradually according to the age group, weeks earlier.

A report from the country’s health ministry, showed that a third dose reduced recipients’ risk of testing positive for SARS-CoV-2 by more than 10 times 2 weeks later. And in In a published pre-publication, researchers used data from a health maintenance organization (HMO) to calculate that a third dose reduces the risk of a person being positive for the virus from one week after the injection by about half and reduces it even more after the second week.

The number of cases and hospitalizations in Israel continues to rise as the variant spreads Delta. But the number of cases in the elderly began to decline in the weeks following July 31, when third doses of the messenger RNA vaccine were offered to people 60 years and older., a sign that the reinforcements can work. On August 29, Israel announced that it would expand the booster program to all people 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 has already announced.

“That boosters can reduce infections is not surprising,” says David Dowdy, an epidemiologist at Johns Hopkins University. “If your goal is to provide someone with high levels of immunity in the short term, there is no doubt that a good way to do that is to use a booster.“, He says. The results also add to the evidence that current vaccines remain effective against the Delta variant. But Dowdy cautions that because the studies only cover a short period after the booster, it is not clear how long the boost in protection will last. A question that alerts on the waves that are predicted by virtue of past experience.

Researchers from Israel’s Ministry of Health and various universities analyzed information on more than 1.1 million Israelis over the age of 60 in the ministry’s database, correlating COVID-19 diagnoses between July 30 and August 22 with data showing if and when people received a booster. Twelve days after receiving a third dose, they found that the risk of infection had decreased by more than 10 times. This brings the protection back to the 95% range seen shortly after the second dose. The effect against severe disease was even greater, reducing the risk by 15 times, but the authors warn that a small number of patients with severe disease and the short duration of the study means the result is very uncertain.

The another study comes from researchers at KSM Research and Innovation at Maccabi Healthcare Services (MHS), the second largest HMO in Israel. They joined researchers at the Yale School of Public Health to see if they could discover an early effect of the boost on the health records of the 2.5 million MHS members, or just over a quarter of the Israeli population.

The team analyzed the results of 182,076 polymerase chain reaction tests performed in 153,753 members MHS older than 40 years during the first 3 weeks of August, compare those who tested negative with those who tested positive. Among 7 and 13 days after a booster dose, the analysis showed that the likelihood of a person testing positive for the coronavirus was reduced by 48% compared to someone who had only received two doses; of 14 to 21 days after injection, the probability was reduced by 70%. The study did not look at serious illnesses, only new infections.

Dowdy says the result is good news, but that doesn’t prove it’s safe to make boosters widely available. “The question is not whether a booster strengthens your immune system in the short term,” he says. But rather if it provides a significant increase in long-term immunity for months- And if so, what is the correct interval for giving the booster shots? The answers to these crucial questions, but they are still totally unknown. “

Daniel Weinberger of Yale, who helped lead the study, agrees. “Our report looked at a very limited problem. Short-term protection “is only one piece of the puzzle,” he explained.

“If the additional immunity of the booster wears off quickly, or if the campaign distracts attention from surveillance efforts or reaching people who have not been vaccinated at all Dowdy explains that the effort will have little impact in the long term. We need longer term data to be sure that we won’t be surprised by new waves and that we will have to work at certain intervals with a correct strategy ”.

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