Israeli study shows real-world efficacy of Pfizer-BioNTech’s COVID-19 vaccine

By Sally Robertson, B.Sc.May 6 2021

Researchers have conducted an analysis of nationwide surveillance data from Israel demonstrating the real-world effectiveness of Pfizer-BioNTech’s BNT162b2 vaccine at protecting against infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the agent that causes coronavirus disease 2019 (COVID-19).

Study: Impact and effectiveness of mRNA BNT162b2 vaccine against SARS-CoV-2 infections and COVID-19 cases, hospitalisations, and deaths following a nationwide vaccination campaign in Israel: an observational study using national surveillance data

The team – from the Israel Ministry of Health in Jerusalem, Pfizer in Collegeville, Philadelphia, and Pfizer Pharmaceuticals Israel in Herzliya – report that marked and sustained declines in the incidence of SARS-CoV-2 infection were observed, including among older adults, as the proportion of individuals vaccinated with two doses of the vaccine began to rise.

Sharon Alroy-Preis and colleagues say the findings demonstrate the beneficial public health impact of a nationwide vaccination campaign and offer hope that immunization against SARS-CoV-2 will eventually control the pandemic.

Writing in The Lancet the researchers say: “These findings are of international importance as vaccination programs ramp up across the rest of the world, suggesting that other countries can similarly achieve marked and sustained declines in SARS-CoV-2 incidence if they can achieve high vaccine uptake.”

Israel launched a campaign to vaccinate 6.5 million people

The Pfizer–BioNTech BNT162b2 vaccine was authorized for emergency use in Israel in December of 2020 after its high efficacy in protecting against symptomatic COVID-19 was demonstrated in a randomized controlled trial of individuals aged 16 years and older.

Following this emergency use authorization, the Israel Ministry of Health launched a nationwide campaign to administer two doses of the vaccine (separated by an interval of 21 days) to the 6∙5 million residents in Israel aged 16 years and older (71% of the population).

By the 3^rd April 2021, 61% of the population had received at least one dose of the vaccine.

Alroy-Preis and colleagues say preliminary estimates of the efficacy of one BNT162b2 dose have been reported from Denmark, Israel, the UK, and the USA, and estimates for two doses have been described for a subset of the Israeli population enrolled in a health maintenance organization.

“However, no estimates of the effectiveness of two doses of BNT162b2 against a range of SARS-CoV-2 outcomes, including among older adults, have been reported,” they add. “Furthermore, population-level estimates of the impact of a COVID-19 vaccine on the incidence of SARS-CoV-2 infections have not been reported.”

What did the researchers do?

Alroy-Preis and colleagues estimated the real-world effectiveness of two doses of BNT162b2 against a range of SARS-CoV-2 outcomes using national surveillance data from the first 4 months (January 24^th to April 3^rd, 2021) of the vaccination campaign.

They compared the incidence rates of SARS-CoV-2 infection (asymptomatic and symptomatic), COVID-19-related hospitalization, severe or critical hospitalization, and death from the disease among fully vaccinated individuals (those for whom 7 days had passed since a second dose) with the rates among unvaccinated individuals.

The researchers also used the proportion of spike gene target failures (SGTF) on polymerase chain reaction (PCR) testing among a nationwide convenience-sample of SARS-CoV-2-positive specimens to estimate the prevalence of the B.1.1.7 variant.

“The SARS-CoV-2 variant B.1.1.7, first identified in the UK and associated with increased transmissibility, has emerged in several countries and was first reported in Israel on December 23^rd, 2020,” says the team.

What did they find?

By the 3^rd April, 4,714,932 (72∙1%) of 6,538,911 people aged 16 years or older had been fully immunized with two doses of BNT162b2.

During the study period, there were 232,268 SARS-CoV-2 infections, 7,694 COVID-19 hospitalizations, 4,481 cases of severe or critical hospitalization, and 1,113 deaths from the disease.

After adjustment for age, sex, and calendar week, the efficacy of complete BNT162b2 vaccination was 95∙3% against SARS-CoV-2 infection overall; 91∙5% against asymptomatic infection, 97∙0% against symptomatic COVID-19, 97∙2% against hospitalization, 97∙5% against severe or critical hospitalization, and 96∙7% against death from the disease.

The estimates of vaccine efficacy against all SARS-CoV-2 outcomes were higher than 96% among people aged 75 years and older.

Across all age groups, as cumulative vaccine coverage increased, the 7-day daily moving average of incident cases of SARS-CoV-2 infection markedly declined, reports the team.

“Notably, steeper and earlier declines were observed in older age groups, which had higher and earlier vaccine coverage,” says Alroy-Preis and colleagues.

The B.1.1.7 variant was the dominant strain

During the analysis period, 94.5% of 8,472 samples tested showed an SGTF, thereby proving that BNT162b2 is effective against the B.1.1.7 variant.

“This study showed that two doses of BNT162b2 were highly effective, including in older adults, against laboratory-confirmed SARS-CoV-2 infections and COVID-19 hospitalizations, severe disease, and deaths in a nationwide observational study where variant B.1.1.7 was the dominant strain,” say the researchers.

Corroborating the observed high effectiveness was an observed marked decline in the incidence of SARS-CoV-2 infection as vaccine coverage increased, adds the team.

What did the authors conclude?

“These data provide nationwide evidence of the beneficial public health impact of a COVID-19 vaccination campaign,” writes Alroy-Preis and colleagues.

“Taken together, these findings suggest that high vaccine uptake can meaningfully stem the pandemic and offers hope for eventual control of the SARS-CoV-2 outbreak as vaccination programs ramp up across the rest of the world,” they conclude.