According to an anticipated study, older Israelis who have had a third dose COVID-19 vaccine are less likely to be positive for SARS or develop severe COVID-19. The study was published on 15 September.
Two doses of messenger RNA-based COVID-19 vaccinations are the standard. However, some governments, including Israel, have begun to administer third booster shots. This latest study analyzed 1.1 million Israelis aged 60 and older who had received their second dose at least five months prior to the current study. Participants who received a third jab 12 days or more after their first two were examined were 19.5 times less likely than those who had only received two jabs.
This is a strong result, according to Susan Ellenberg, a biostatistician from the University of Pennsylvania in Philadelphia. She also said that the data may be the strongest she's seen for boosters. However, there are potential biases in data that could make it difficult for scientists to conclude that boosters are needed for all populations. The data also do not address concerns about vaccine equity as billions of people still wait for their first shot.
Israel got an early start in vaccinating its citizens. In July, the PfizerBioNTech vaccine was offered to third-dosers for people over 60. According to the latest analysis, the third jab is associated with a significant decrease in severe COVID-19 and a 11.3-fold decrease in SARS-CoV-2 infection.
Ellie Murray, an epidemiologist from Boston University, Massachusetts warns that observational studies like this one can have biases that are hard to detect and account for. People who sign up for a booster may have a higher risk of COVID-19 or behave differently than people who don't get it.
Ellenberg claims that authors attempt to correct some of these biases. Ellenberg says that even if all biases are not eliminated, the strength of the effect suggests that the booster provides some protection at least for the short-term. The study authors could not be reached prior to publication.
Global ramifications
These findings are coming as wealthy countries consider offering booster shots. On 17 September, an advisory committee of US Food and Drug Administration will discuss Pfizers' application for supply boosters in the United States. The committee will be presented data by one of the Israeli authors.
Murray claims that there is no need to boost vaccines because of the possible biases in the data and the insufficient evidence that waning immunity occurs after vaccination. She says that it is more important to get more people vaccinated, than to increase the effectiveness of the vaccine by a few percentage point in those who have received the vaccine.
Murray is not the only one to find insufficient evidence in Israel to support boosters. A review by two FDA scientists, published on September 13, cites a preprint from the study. It notes that the Israeli short-term protective effect does not necessarily translate into long-term benefits.
Dvir Aran is a biomedical data scientist at TechnionIsrael Institute of Technology, Haifa. He says Israel has used boosters to stop the transmission of HIV to younger people, and to prevent severe diseases and death in older people.
It is the best method? He says that a two-week lockdown might have produced a similar result. It is an interesting approach to try and stop an epidemic like this by vaccinations.
This article was published with permission on September 16, 2021.
