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

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

Several vaccines against COVID-19 have now been approved 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 the 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 more than doubled cases and hospitalizations in mid-January 2021. In response, the country declared a closure on January 8. of 2021. However, the cases were not reduced and there were questions about the effectiveness of the vaccine.

However, it is a challenge to estimate the effectiveness of vaccines in the real world. Vaccination uptake is framed in the socioeconomy and demographics of a population, along with disparities between groups in infection rates. These confounders are not present in randomized clinical trials due to blinding. In the real world, individual clinical and demographic data are needed to determine the effectiveness of the vaccine.

Estimation of vaccine efficacy

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

The author used positive cases and daily hospitalization data from the Israeli Ministry of Health’s public database COVID-19, including hospitalization after vaccination until January 31, counted the number of individuals vaccinated each day and multiplied it by the daily case rate of the population as a whole, 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 there were 3,082,190 people who were 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 vaccines, 1,215,797 were over 60 years old.

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

This analysis is based on the assumption that all people who received the early vaccines 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.

Adjusting for this, the author found that if the vaccinated population is assumed to have half the number of cases than the general population, there is no decrease in the number of cases up to 21 days after the first dose. The number of cases decreased by 66% seven days after the second dose.

For people over 60, who account for a significant proportion of severe cases of the disease, the analysis suggests a strong effect of the vaccine, reducing severe cases by approximately 60% after the first dose and up to 94% seven. days after the second dose.

Estimates of vaccination efficacy rate for different levels of beta values. Standard errors are in the shadows.

Highly effective vaccine in the real world

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

According to clinical trials, the Pfizer vaccine was reported to be 95% effective one week after the second dose, although the previous efficacy is unclear. Analysis of Israel’s real-world data, which includes approximately 140 times more people 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 case reporting, the fact that hospitalization may increase the count of cases observed, and limitations in making inferences at the individual level as an analysis used to group counts. Because the incidence in the general population is also affected by vaccination, the actual efficacy may be higher. The author writes that the analysis provides “great security” that the vaccine is highly effective.

* Important news

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