The further the SARS-CoV-2 coronavirus spreads, the more common mutations become. What does this mean for the effectiveness of the vaccinations? For the particularly easily transferable variant B.1.1.7, which was identified in Great Britain in September 2020, researchers can now give the all-clear: Laboratory studies indicate that the BioNTech vaccine also offers sufficient protection against this variant. For the mutations from South Africa and Brazil, however, the study situation has so far been less good. Pre-published data paint a mixed picture.
The vaccines against SARS-CoV-2 train the immune system to recognize and react to certain surface structures of the coronavirus. The so-called spike proteins with which the virus docks to cells in order to penetrate them are particularly important. Mutations also change these proteins, which are intended to serve as a distinguishing feature for the immune system trained by the vaccination. Various mutations are now known, including from Great Britain, South Africa and Brazil, which are beginning to spread worldwide.
Protection against British mutation likely
A team led by Alexander Muik from BioNTech has now tested in a laboratory study to what extent the vaccine developed by the company also against the British coronavirus variant B.1.1.7. immunized. To do this, they generated pseudoviruses that carried the characteristics of the original strain from Wuhan or the mutations of variant B.1.1.7. exhibited. In contrast to real viruses, the viruses used for the laboratory experiment could not multiply. Using the blood serum from 40 people who received the BioNTech vaccine during the clinical trials, the researchers tested to what extent the antibodies in the blood could neutralize the two different types of pseudoviruses.
Their result: the vaccinee’s blood serum did not neutralize the mutated viruses quite as effectively as the original strain, but still enough to likely ensure immunity. Compared to the Wuhan variant, the titer was about 20 percent lower. “Based on experience with influenza vaccines, a titer reduced by 20 percent does not indicate a biologically significant change in neutralization activity,” the researchers said. “That makes it unlikely that the British virus variant will evade the protection provided by the BioNTech vaccine.”
Further mutations could affect immunity
In a previous study, which was published on the preprint server BioRxiv, researchers working with Xuping Xi from the University of Texas had tested the extent to which the antibodies in the blood of vaccinated persons react to a certain change in the spike protein. This mutation, called N501Y, occurs in both the British and South African variants of the coronavirus. The results of this study had already indicated that the neutralizing effect would have to be sufficient to fend off mutated viruses.
In contrast to Muik’s study, this only dealt with a single mutation. “The question remained whether a virus with the full set of mutations in line B.1.1.7, each of which can potentially disrupt antibody binding, would be efficiently neutralized by the immune sera of the vaccinated,” the researchers said.
Even if they were able to confirm this for B.1.1.7, the same question remains for the South African mutant. In addition to N501Y and other changes, this has the so-called E484 mutation, which it shares with the Brazilian variant of the virus. According to a previously published study by Allison Greaney from the University of Washington in Seattle, this mutation reduced the neutralizing effect of antibody sera by a factor of ten in laboratory tests. However, this does not mean that the vaccine or the immunity acquired through an infection against virus variants with this mutation are ten times less effective – after all, the immune system usually does not only react to this one structure of the virus.
Adaptation of the vaccine is conceivable
In Brazil, however, several reinfections have already been observed in which people who had gone through Covid-19 became infected with the new variant of the virus and fell ill again. This suggests that so-called escape mutations occur, in which the virus changes in regions with high population levels in such a way that it can continue to infect people. The more people are infected with SARS-CoV-2, the higher this risk.
In view of such developments, Muik and colleagues write: “Although the ongoing neutralization of the current B.1.1.7 variant is reassuring, preparation for a possible COVID-19 vaccine strain change must be prepared.” They consider themselves well equipped for this step. “The flexibility of the mRNA-based vaccine technology makes it easier to adapt the vaccine to a new virus strain,” the researchers said.
Sources: Alexander Muik (BioNTech) et al., Science, doi: 10.1126 / science.abg6105; Xuping Xie (University of Texas) et al., BioRxiv Preprint, doi: 10.1101 / 2021.01.07.425740; Allison Greaney (University of Washington, Seattle) et al., BioRxiv Preprint, doi: 10.1101 / 2020.12.31.425021