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

Using public data from Israel’s 2019 coronavirus disease (COVID-19), a study suggests that the BioNTech-Pfizer BNT162b2 vaccine is very effective in the real world.

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

By the time 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 the 8th. January 2021. But, the cases did not go down and there were questions about the effectiveness of the vaccine.

However, it is difficult to estimate the effectiveness of vaccines in the real world. The use of vaccination is linked to the socio-economy and demographics of a population, as well as to disparities between groups in infection rates. These confounding factors are not present in randomized clinical trials due to blinding. In the real world, individual clinical and demographic data are needed to determine vaccine efficacy.

Estimation of vaccine efficacy

In an article published on the medRxiv * pre-print server, Assistant Professor Dvir Aran, Technion-Israel Institute of Technology, used publicly available data on COVID-19 cases and hospitalization following Pfizer vaccine vaccination. The author provides estimates of the effectiveness of vaccines in reducing cases.

The author used daily positive cases and hospitalization data from the Israeli Ministry of Health’s public COVID-19 database, including hospitalization after vaccination until January 31, counting the number of people vaccinated each day and multiplied that by the overall daily case rate. population, adjusting for the difference in the number of cases between the vaccinated population and the general population. Using these parameters, the author estimated the efficacy of the vaccine.

The analysis found that 3,082,190 people had been 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 vaccinated, 1,215,797 were over 60 years old.

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

This analysis is based on the assumption that all people who received their vaccines early had the same level 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.

Taking this into account, 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, who represent a major proportion of critically ill cases, analysis suggests a strong effect of the vaccine, reducing severe cases by about 60% after the first dose and up to 94% on seven days after the second dose.

Estimates of the efficacy rate of vaccination by different levels of beta values. Standard errors are in the dark.

Very effective vaccine in the real world

Overall, the analysis suggests a reduction in positive cases of 66-83% in people over 60, 76-85% in under 60, and 87-96% effective in prevention severe cases.

The Pfizer vaccine is said to be 95% effective one week after the second dose based on clinical trials, although the effectiveness before that is unclear. Analysis of actual data from Israel, which includes around 140 times more individuals than the trial, provides an estimate of the vaccine’s effectiveness in reducing cases and severity of the disease.

The author recognizes certain limitations of the analysis. These include delays in reporting cases, as hospitalization can increase the number of cases observed, and limitations in making inferences at the individual level as the analysis used to aggregate the numbers. As the incidence in the general population is also affected by vaccination, the actual effectiveness may be higher. The author writes that the analysis provides “strong assurance” that the vaccine is very effective.

*Important Notice

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