How effective has the COVID-19 vaccination program been in Israel?

Using publicly available data from the 2019 coronavirus disease (COVID-19) from Israel, a study suggests that the BioNTech-Pfizer BNT162b2 vaccine is proving to be highly effective in the real world.

Several vaccines have now been approved for COVID-19 and many countries have started intensive vaccination programs. In Israel, vaccination began on December 20, 2020. By the end of January, 33% of the population had received their first dose of the BioNTech-Pfizer vaccine, also known as BNT162b2, and 19% had received their second dose.

Just as vaccinations began, the country was in the midst of a third wave of COVID-19, with cases and hospitalizations more than doubling by mid-January 2021. In response, the country declared a lockdown on January 8, 2021. However, cases did not come. down and there were questions about the effectiveness of the vaccine.

However, it is challenging to estimate how effective vaccines are in the real world. Vaccination uptake is intertwined with a population’s socioeconomic and demographics, along with intergroup differences in infection rates. Such confounding factors are not present in randomized clinical trials due to blinding. In the real world, clinical and demographic data at the individual level are needed to determine the effectiveness of vaccines.

Estimate vaccine effectiveness

In a paper published on the medRxiv * preprint server, assistant professor Dvir Aran, of the Technion-Israel Institute of Technology, used publicly available data on COVID-19 cases and hospitalization following vaccination with the Pfizer vaccine. The author provides estimates of the effectiveness of vaccines in reducing cases.

The author used the daily positive cases and hospital admission data from the public database COVID-19 of the Israeli Ministry of Health, including hospital admission after vaccination until January 31, counted the number of individuals vaccinated each day and multiplied that by the daily number of cases in the population as a whole. , adjusted for the difference in the number of cases between the vaccinated and the general population. Using these parameters, the author estimated the effectiveness of the vaccine.

The analysis found that there were 3,082,190 people vaccinated with a first dose between December 20, 2020 and January 31, 2021, and 1,789,836 had also received their second dose. Of the total number of vaccinated 1,215,797 were older than 60 years.

Of the vaccinated individuals, 31,810 tested positive for SARS-CoV-2 and 1,525 were hospitalized or died. The analysis indicates that for those over 60 years old, the number of cases decreased by approximately 28% on day 13 after the first dose, a 43% decrease between days 14 and 21 and a decrease of more than 80% after the second dose .

This analysis is based on the assumption that all people who initially received their vaccine had the same number of positive cases as the general population. But this is not true in the real world. Older people have lower positivity and lower socioeconomic groups have higher positivity rates.

Corrected for this, the author found that assuming that the vaccinated population has half the number of cases as the general population, there is no decrease in the number of cases until 21 days after the first dose. The number of cases decreased by 66% seven days after the second dose.

For people over 60 years of age, who make up the majority of severely ill cases, the analysis suggests a strong effect of the vaccine, with severe cases occurring by about 60% after the first dose and up to 94% seven days after the second dose. reduced.

Effectiveness estimates of the vaccination by different levels of beta values. Standard errors are in the shadows.

Vaccine very effective in the real world

Overall, the analysis suggests a 66-83% reduction in the number of positive cases in people over 60 years old, 76-85% for those under 60 years old, and 87-96% effective in preventing severe cases.

The Pfizer vaccine is reported to have 95% efficacy one week after the second dose based on the clinical studies, although the efficacy is not clear before. Analysis of the real world data from Israel, which includes approximately 140 times more individuals than the trial, provides an estimate of the vaccine’s effectiveness in reducing cases and the severity of the disease.

The author acknowledges some limitations of the analysis. These include delays in reporting cases, the fact that hospitalization can increase the number of cases observed, and limitations in making inferences at the individual level as the analysis used to aggregate counts. Since the incidence in the general population is also affected by vaccination, the true effectiveness may be higher. The author writes that the analysis provides “strong reassurance” that the vaccine is highly effective.

*Important announcement

medRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, serve clinical practice / health-related behavior, or be treated as established information.