Talia Kustin, Noam Harel, Uriah Finkel, Shay Perchik, Sheri Harari, Maayan Tahor, Itamar Caspi, Rachel Levy, Michael Leschinsky, Shifra Ken Dror, Galit Bergerzon, Hala Gadban, Faten Gadban, Eti Eliassian, Orit Shimron, Loulou Saleh, Haim Ben-Zvi, Doron Amichay, Anat Ben-Dor, Dana Sagas, Merav Strauss, Yonat Shemer Avni, Amit Huppert, Eldad Kepten, Ran D. Balicer, Doron Nezer, Shay Ben-Shachar, View ORCID Profile Adi Stern
The SARS-CoV-2 pandemic has been raging for over a year, creating global detrimental impact. The BNT162b2 mRNA vaccine has demonstrated high protection levels, yet apprehension exists that several variants of concerns (VOCs) can surmount the immune defenses generated by the vaccines. Neutralization assays have revealed some reduction in neutralization of VOCs B.1.1.7 and B.1.351, but the relevance of these assays in real life remains unclear. Here, we performed a case-control study that examined whether BNT162b2 vaccinees with documented SARS-CoV-2 infection were more likely to become infected with B.1.1.7 or B.1.351 compared with unvaccinated individuals. Vaccinees infected at least a week after the second dose were disproportionally infected with B.1.351 (odds ratio of 8:1). Those infected between two weeks after the first dose and one week after the second dose, were disproportionally infected by B.1.1.7 (odds ratio of 26:10), suggesting reduced vaccine effectiveness against both VOCs under different dosage/timing conditions. Nevertheless, the B.1.351 incidence in Israel to-date remains low and vaccine effectiveness remains high against B.1.1.7, among those fully vaccinated. These results overall suggest that vaccine breakthrough infection is more frequent with both VOCs, yet a combination of mass-vaccination with two doses coupled with non-pharmaceutical interventions control and contain their spread.
Mass vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently underway worldwide, providing hope that the COVID-19 pandemic may soon be mitigated. In Israel, vaccination commenced on December 20, 2021, primarily with the BNT162b2 mRNA vaccine, and by mid-March 2021, over 80% of the eligible population (all individuals 16 years old and above) were vaccinated with at least one dose. In clinical trials, the BNT162b2 mRNA vaccine was shown to be 95% efficacious in preventing symptomatic disease; a similarly high protective effectiveness has also been found in real-world settings in Israel [1, 2]. However, concerns have emerged regarding the effectiveness of vaccines against various SARS-CoV-2 strains. In particular, three strains have been recently defined as “variants of concern” (VOC) by the world health organization (WHO; www.who.int): the B.1.1.7 strain (originally detected in the United Kingdom), the B.1.351 strain (originally detected in South Africa), and the P.1 strain (originally detected in Brazil). Accumulating evidence suggests that the B.1.1.7 strain spreads more rapidly than the original circulating strain and is accompanied by increased mortality rates [3, 4].
Concerns have emerged that the B.1.351 and P.1 strains are able to overcome previous immunity to SARS-CoV2 [5, 6], yet the evidence has been somewhat mixed. Using engineered viruses and/or sequences, laboratory studies have shown that neutralization of B.1.1.7 by BNT162b2 vaccine-elicited sera was either similar or slightly reduced as compared to neutralization of the original circulating strain. Conversely, a significant reduction in neutralization of B.1.351 was observed [7-11], while other studies suggested neutralization remained relatively high against both B.1.1.7 and B.1.351 . T-cell responses, which are not captured by neutralization studies, were also shown to remain stable against these variants following vaccination . Thus, it remains unknown whether VOCs can perform BNT162b2 vaccine breakthrough in real world settings, in which the vaccine mainHere we tested the hypothesis that the B.1.1.7 and B.1.351 strains are able to overcome BNT162b2 mRNA vaccine protection. To this end, we identified individuals with documented SARS-CoV-2 infection – symptomatic or asymptomatic (hereby denoted as carriers) amongst members of the Clalit Health Services (CHS), the largest health care organization in Israel, which insures 4.7 million patients (53% of the population). We focused on vaccinated carriers, divided into two categories: (a) individuals who had a positive PCR test that was performed between 14 days after the 1st dose and a week after the 2nd dose (denoted as partial effectiveness, PE), and (b) individuals who had a positive PCR test that was performed at least one week after the second vaccine dose (denoted as full effectiveness, FE). Each vaccinee (case) was matched with an unvaccinated carrier (control) with similar demographic characteristics (date of PCR, age, sex, ethnic sector, and geographic location) to reduce bias associated with differential exposure (Methods). Next, we collected RNA from the PCR samples and performed complete viral genome sequencing for 813 samples from different individuals, consisting of 149 pairs of FE-controls, 247 pairs of PE-controls and additional samples whose match did not undergo successful sequencing (see below) (Table 1, Table S1, Fig. S1). When examining the results, it became evident that B.1.1.7 was the predominant strain of virus in Israel over the entire sampling period, increasing in frequency over time (Fig. 1A). Conversely, the B.1.351 strain was at an overall frequency of less than 1% in our sample, confirming previous reports (Fig. 1B) . No other variants of concern or variants of interests, as defined by the WHO, were found in our sample (Fig. S2). We collectively denote all other lineages found as wild-type (WT) (Methods). Moreover, we did not find evidence for the increased presence of any additional mutations that are not lineage defining mutations of B.1.1.7 or B.1.351.
We next analysed our paired set of vaccinated and non-vaccinated carriers, using a stringent method of lineage assignment for each viral sequence (Methods). Based on previous results from neutralization assays, we hypothesized that B.1.1.7 may be slightly vaccine-resistant as compared to WT, whereas B.1.351 may be more vaccine-resistant when compared to both B.1.1.7 and WT. Under this hypothesis of ordered resistance, we performed our statistical analyses first on the B.1.1.7 strain, while excluding B.1.351 strains (to avoid obscuring a potential signal), and then compared the B.1.351 with the B.1.1.7 and WT variants combined (Fig. 2).