Israelis who received their final COVID-19 vaccination jab more than five months ago have a higher chance of testing positive for coronavirus compared to those who received their jabs at a later date, a study published this week by the Leumit Health Services shows.
The Leumit sample included 28,064 double-vaccinated Israeli adults of different ages who had never contracted the virus. They were administered PCR tests in order to find out how the passage of time affected the vaccine’s ability to prevent infection, i.e. the transmissibility of the virus.
The study began on June 1, when the highly contagious Delta variant became the dominant strain in Israel.
Data showed that Israelis who were vaccinated more than 142 days before being tested were about twice as likely to be positive compared to others who received their jabs at a later date, with a total of 423 (1.5%) testing positive for coronavirus.
In the 60 and older age group, 2% of the 6,278 Israelis who got their shots 142 days earlier tested positive for the virus. In contrast, of the 1,348 who received their jabs later, only 1% were infected. Despite this being a small sample size for definitive results, the study suggests that vaccinated Israelis over the age of 60 were 1.92 times more likely to contract the coronavirus if five months had passed since their two shots.
Israelis between the ages of 40-59 whose jabs date back to January were 2.1 times more likely to get infected compared to others in their age bracket who received the vaccine shots at a later date. For Israelis younger than 39 who received their jabs more than 142 days before being tested, the chances of getting infected with COVID were 1.6 times higher.
Leumit researchers emphasized that the results add more impetus to the need to purchase more doses and begin administering a booster shot.
The study did not say whether this drop in protection also impacts the vaccine’s clinically tested purpose – to protect against severe symptoms of the COVID-19 respiratory disease. According to multiple studies, this protection remains roughly the same even after six months.