A nationwide case-control study conducted in France has assessed the efficacy of mRNA-based coronavirus disease 2019 (COVID-19) vaccines against original severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants, including B.1.1.7, B.1.351, and P1.

In real-life pandemic situations, the two-dose regimen of mRNA vaccines has shown equivalent protective efficacy against the original virus and B.1.1.7 variant and a slightly reduced efficacy against the B.1.351 and P1 variants. The study has recently been published in the journal The Lancet Regional Health – Europe.  

Background

Within one year of the emergence of the COVID-19 pandemic, several potent vaccines were been developed against the original Wuhan strain of SARS-CoV-2. However, with the progression of the pandemic, multiple viral variants with significantly high infectivity have emerged and soon become predominant in many countries worldwide. This has raised global concern about the efficacy of preexisting vaccines against newly emerged viral variants.

In real-world pandemic situations, most COVID-19 vaccines have shown equivalent efficacy against the original SARS-CoV-2 and the B.1.1.7 variant, which was first identified in the UK. However, in general, antibodies induced by vaccination or natural infection have shown significantly lower efficacy in neutralizing the B.1.351 and P1 variants, which were first identified in South Africa and Brazil, respectively. The presence of E484K and K417N spike mutations in the B.1.351 variant and E484K and K417T spike mutations in the P1 variant has been attributed to their immune evasion abilities.

In the current study, the scientists have assessed the efficacy of a two-dose regimen of mRNA-based COVID-19 vaccines against predominantly circulating variants in France, which are mostly original SARS-CoV-2 and variants B.1.1.7, B.1.351, and P1.

Study design

This nationwide case-control study was conducted on 7,288 adults infected with the original SARS-CoV-2 virus, 31,313 with the B.1.1.7 variant, 2,550 with the B.1.351/P1 variants. In addition, 3,644 non-infected individuals were included as controls. All participants were asked to complete an online survey questionnaire designed to collect information about sociodemographic characteristics, preexisting health conditions, recent SARS-CoV-2 testing results, recent activity-related viral exposures, and vaccination details.

Specifically, the scientists aimed to evaluate the efficacy of two mRNA vaccines, BNT162b2 (Pfizer/BioNTech) and mRNA-1273 (Moderna), in real-world pandemic settings. However, because of a lack of information about vaccination, they could determine the efficacy of two vaccines separately.

To genetically identify viral variants, all SARS-CoV-2 positive samples were further analyzed by screening reverse transcription-polymerase chain reaction (RT-PCR).

Important observations

Based on the survey findings, the susceptibility to acquiring B.1.1.7 or B.1.351/P1 infection was relatively higher among male participants, non-healthcare workers, and those with higher educational levels. Moreover, a significantly higher susceptibility to acquiring B.1.351/P1 infection was observed among participants even after receiving two doses of mRNA vaccines.

The findings of multivariable statistical analysis identified a significant correlation between the increased risk of infection and a history of chronic respiratory disease, lower education level, larger household size, having school/daycare center-attending children in the household, or being a healthcare worker. Importantly, a history of high blood pressure and diabetes was found to be associated with a lower risk of infection with the B.1.1.7 variants.  

Protection from natural infection and vaccination

A recent history of PCR-confirmed SARS-CoV-2 infection (2 – 6 months) was found to be 83% – 88% protective against all tested viral variants. Similarly, a relatively distant history of SARS-CoV-2 infection (more than 6 months) was found to be 74% – 84% protective against all viral variants

The protective efficacy of mRNA vaccines 7 days after the 2^nd dose was found to be 88% against the original SARS-CoV-2, 86% against the B.1.1.7 variant, and 77% against the B.1.351/P1 variants.

Importantly, further statistical analysis identified that “being a healthcare worker” is a major confounding factor affecting the estimation of vaccine efficacy against SARS-CoV-2 infection.

Study significance

The study reveals that mRNA-based COVID-19 vaccines are highly effective in reducing the risk of infection by SARS-CoV-2 and its major variants; thus, highlighting the importance of mass vaccination programs in combating the COVID-19 pandemic.  

Written by

Dr. Sanchari Sinha Dutta

Dr. Sanchari Sinha Dutta is a science communicator who believes in spreading the power of science in every corner of the world. She has a Bachelor of Science (B.Sc.) degree and a Master's of Science (M.Sc.) in biology and human physiology. Following her Master's degree, Sanchari went on to study a Ph.D. in human physiology. She has authored more than 10 original research articles, all of which have been published in world renowned international journals.