Vaccination efforts have rolled out in many countries worldwide. One of the vaccines authorized is the BNT162b2 or the Pfizer-BioNTech vaccine, a messenger ribonucleic acid (mRNA) vaccine against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes the coronavirus disease (COVID-19).
Researchers at the Pitié Salpêtrière Hospital, Department of Virology, Paris, France determined that in BNT162b2-vaccinated participants who received two doses, their sera harbored at least a neutralizing titer against the three SARS-CoV-2 variants.
The study findings, which appeared in the pre-print server bioRxiv*, suggest a particular humoral protection activity on the United Kingdom or South African variants after two-doses of the mRNA-vaccine.
One of the drawbacks of vaccine development is its capacity to protect against the mutated virus. It took a year to develop effective and safe vaccines against SARS-CoV-2, and if new variants are spreading, it may take longer to create updated vaccines.
Hence, scientists wanted to determine if the currently developed and authorized vaccines can protect against these new variants.
Since October 2020, three new variants have emerged from the gene encoding the Spike (S) protein of SARS-CoV-2. The new variants include the United Kingdom (U.K.) variant B.1.1.7 with many mutations in the fall of 2020 and the South African variant called B.1.351. Another recent variation has emerged, which is called the Brazil variant or P.1.
The new variants caused skyrocketing cases as they appear to be more transmissible. Recent studies have also shown that the U.K. variant may also cause more severe illness. However, further investigations are ongoing.
These variants harbor a specific pattern of deletion and mutations, including amino-acid replacements at key sites in the S Receptor Binding Domain (RBD).
As vaccination efforts continue, the question remained whether these variants could evade the neutralizing antibodies (NAb) induced by the mRNA vaccine.
Two recent studies have shown that only some mutations from the U.K. and S.A. variants showed weaker neutralization capacity of vaccine-elicited sera. Another study tested SARS-CoV-2-S pseudoviruses containing either the ancestral Wuhan reference strain or the U.K. spike protein with BNT162b2 vaccine-elicited sera revealed slightly reduced primarily reserved neutralizing titers against the U.K. pseudovirus. However, none of these studies were performed on clinical isolates containing the two strains' full genomic mutations.
To answer the question, the researchers conducted a virus neutralization test (VNT) on sera from healthcare workers with either previous mild infection of COVID-19, either the predominant D614G strain, the U.K. strain, and the S.A. strain.
Two sets of healthcare workers were observed – a convalescent group of 15 participants infected with COVID-19 and a vaccinated group of 29 participants without any history of COVID-19.
The team collected convalescent sera six months after the onset of symptoms from healthcare workers with a positive reverse transcriptase-polymerase chain reaction (RT-PCR) test. They also collected sera from those who had the vaccine three weeks after the first dose and seven days after the booster shot.
From there, the team used the SARS-CoV-2 anti-nucleocapsid (N) immunoglobulin G (IgG) assay, called the Alinity SARS-CoV-2 IgG assay by Abbott Laboratories. Further, the team also obtained and isolated SARS-CoV-2 clinical isolates D614G, U.K., and S.A. Then, the team determined the neutralizing activity of the various serum specimen.
The team found that most sera obtained contain neutralizing antibody titers, suggesting central humoral protection against either of the two variants. But, after six months post-infection, some HCWs showed no neutralizing activity against the S.A. strain.
The study findings showed that even those with COVID-19 mild infection may still need to get the vaccine for protection.
The team suggests that further studies are needed to determine the SARS-CoV-2 correlates of vaccine-induced protection based on Nab and T cell responses.
They suggested that further studies are required to determine the SARS-CoV-2 correlates 157 of vaccine-induced protection based on NAb and T cell responses.
"The long-term evaluation regarding the lasting of NAb induced by vaccination is needed to assess the durability of protection against SARS-CoV-2 variants," the team added.
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.