In keeping with CDC research, Israeli information means that mass vaccinations resulted in a lower in extreme Covid instances

An Israeli health worker from Maccabi Healthcare Services prepares to administer a dose of the Pfizer BioNtech vaccine in Tel Aviv on February 24, 2021.

Jack Guez | AFP | Getty Images

Data from Israel, which vaccinated the vast majority of its elderly population with the Pfizer Covid-19 vaccine, suggests that mass vaccination has prevented people from getting seriously ill, according to a new study by the Centers for Disease Control and Prevention.

While clinical studies have shown the Pfizer BioNTech vaccine to be 95% effective at preventing Covid-19, the Israeli data provide early insight into the vaccine’s effectiveness in an uncontrolled, real-world setting.

The study, published Friday in the CDC’s weekly report on morbidity and mortality, found that among the most vaccinated portion of the Israeli population, the percentage of patients requiring ventilation has dropped dramatically, suggesting a reduction in the serious illness.

“Taken together, these results suggest a reduced rate of severe COVID-19 after vaccination,” wrote researchers from Ben Gurion University in the Negev, Tel Aviv University and Maccabi Healthcare Services.

Israel launched its national vaccination campaign in December, prioritizing people aged 60 and over, healthcare workers and people with comorbid illnesses. By February, according to the researchers, 84% of the population aged 70 and over had been fully immunized with the Pfizer-BioNTech two-shot vaccine. Only 10% of the population under the age of 50 had been vaccinated at any one time, the researchers said.

The researchers compared the number of Covid-19 patients aged 70 and over who needed a mechanical ventilator with those under 50 who needed a ventilator. The researchers said they needed a ventilator, a medical tool that helps patients breathe, to measure severe Covid-19.

Between October and February, the number of patients aged 70 and over who needed a ventilator decreased. At the same time, the number of people under the age of 50, a generally unvaccinated population, who needed a ventilator, the study found. The country began using gunshots on mostly elderly people on December 20. A second round of shooting followed three weeks later.

The researchers noted some limitations to the study. Israel put in place a strict national stay-at-home order on Jan. 8, weeks after the vaccination campaign began, which could have resulted in a decline in seriously ill patients who would have needed ventilators. The introduction of new variants of the coronavirus could also have affected the data.

The researchers said their results are preliminary, “important evidence of the effectiveness of vaccines in preventing severe cases of COVID-19 at the national level in Israel”.

“Getting COVID-19 vaccines to eligible individuals can help limit the spread of disease and potentially reduce the incidence of serious diseases,” they write.