Preliminary results show Pfizer vaccine's effectiveness in Israel

A snapshot of the results of Israel's national vaccination campaign indicates that the Pfizer-BioNTech vaccine has dramatically reduced the number of cases of COVID-19, the number of hospitalizations and the number of critically ill patients. 

The real-time study of the vaccination campaign was carried out by a group of Israeli scientists and published Feb. 9 on medRxiv, a preprint server for health sciences, operated by Cold Spring Harbor Laboratory in New York.

Israel launched its mass vaccination effort Dec. 22, 2020, starting with people older than 60, nursing home residents, health care workers and people with severe co-morbidities. The vaccine used was BNT162b2, developed by BioNTech in cooperation with Pfizer. It is described as "a lipid nucleoside-modified RNA vaccine, encoding the SARS-CoV-2 full-length spike."

The researchers report that about six weeks after the beginning of the vaccination campaign, "with 80% of individuals older than 60 already vaccinated [Feb. 6, 2021], there was an approximately 49% drop in number of cases, a 36% drop in COVID-19 related hospitalizations and a 29% drop in critically ill patients compared to 21 days ago."

They conclude that although other factors may have influenced these results, "these patterns are driven to a considerable degree by the vaccines."

The study's "real-world" data, the researchers state, show that the drop in Israeli cases and hospitalizations occurred 21 days after the beginning of the vaccination campaign. This is a longer period of time than previous studies had indicated. The researchers speculate a few possible causes of this time lag.

First, logistics in Israel's rapid campaign may have been "imperfect," thus decreasing effectiveness. Second, the older population that the campaign prioritized may have some immune response deterioration. Third, more virulent strains of COVID-19 currently circulating in Israel could have lessened the vaccine effectiveness. Fourth, vaccinated individuals could have let their guard down about using preventive measures.

Israel has the world's highest rate of vaccinated people per capita, the study says, "45.3% and 29.7% of the population having received the first or the second vaccine dose, respectively, or recovered from COVID-19" by Feb. 6. By that date, 89.9% of people over 60 had received their first vaccine dose, and 80% had received both doses.

What the study examined 

To distinguish the effect of the vaccinations from other factors, the study compared changes in COVID-19 incidence in population groups older than and younger than 60, in people living in early-vaccinated cities and late-vaccinated cities, in different geographical areas, and after different lockdown periods.

The decrease in COVID-19 cases and hospitalizations, the study found, "was larger and earlier in older adults compared to younger individuals, who were only recently eligible to receive the vaccine." 

The cities vaccinated earlier also had a "larger and earlier decrease in the number of COVID-19 cases and hospitalizations of individuals 60 years old and older." The same was true in the geographical areas that were vaccinated earlier.

When the researchers compared COVID-19 statistics after lockdowns, the decline in cases of older people was evident only after the third lockdown period that occurred in January, about three weeks after the vaccination campaign started.

A preliminary study

The researchers note that this is a preliminary study, "demonstrating first signs of real-life effectiveness of a national vaccination campaign" with "major public health implications for the struggle against the COVID-19 pandemic." 

They conclude: "More studies aimed at assessing the effectiveness of the vaccination on reducing the transmission of SARS-CoV are needed both on the individual and on the population level with larger longitudinal follow-up and in additional populations."

The research group included scientists from the Weizmann Institute of Sciences, the Institute of Diabetes, Endocrinology and Metabolism, Tel Aviv University and Technion-Israel Institute of Technology.