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The COVID vaccine is less effective against SARS-COV-2 variant B.1.351. The virus will continue to evolve. Pfizer is working to adapt the vaccine.


A study of neutralizing antibodies to SARS-COV-2 variants in vaccinated people and those who had recovered from natural infection was published in “Nature Medicine” on March 26, 2021. The conclusions of the study are troubling: vaccination (from Pfizer) produced less neutralizing antibody against the B.1.351 variant from South Africa, suggesting that it will be less effective.

The abstract of the study is worth quoting in full:

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.7 and B.1.351 variants were first identified in the United Kingdom and South Africa, respectively, and have since spread to many countries. These variants harboring diverse mutations in the gene encoding the spike protein raise important concerns about their immune evasion potential. Here, we isolated infectious B.1.1.7 and B.1.351 strains from acutely infected individuals. We examined sensitivity of the two variants to SARS-CoV-2 antibodies present in sera and nasal swabs from individuals infected with previously circulating strains or who were recently vaccinated, in comparison with a D614G reference virus. We utilized a new rapid neutralization assay, based on reporter cells that become positive for GFP after overnight infection. Sera from 58 convalescent individuals collected up to 9 months after symptoms, similarly neutralized B.1.1.7 and D614G. In contrast, after 9 months, convalescent sera had a mean sixfold reduction in neutralizing titers, and 40% of the samples lacked any activity against B.1.351. Sera from 19 individuals vaccinated twice with Pfizer Cominarty, longitudinally tested up to 6 weeks after vaccination, were similarly potent against B.1.1.7 but less efficacious against B.1.351, when compared to D614G. Neutralizing titers increased after the second vaccine dose, but remained 14-fold lower against B.1.351. In contrast, sera from convalescent or vaccinated individuals similarly bound the three spike proteins in a flow cytometry-based serological assay. Neutralizing antibodies were rarely detected in nasal swabs from vaccinees. Thus, faster-spreading SARS-CoV-2 variants acquired a partial resistance to neutralizing antibodies generated by natural infection or vaccination, which was most frequently detected in individuals with low antibody levels. Our results indicate that B1.351, but not B.1.1.7, may increase the risk of infection in immunized individuals.

(I have added emphasis to some statements in order to make a point)

The South African variant may escape antibodies produced by vaccination in some cases, leading to productive infection. A Pfizer press release claims that the vaccine is fully effective against this variant, although it admits that antibody levels are lower.

The presence of lower neutralizing antibody titers warns us that a new vaccine will be necessary in a few months. Officials are saying that a “booster” shot will be given in six months to a year after the initial two-dose vaccination. They have not stated what the booster would consist of, but it is clear that the vaccine will have to be changed to reflect the RNA sequence of the South African variant and possibly other variants that will appear in the next few months.

<p value="<amp-fit-text layout="fixed-height" min-font-size="6" max-font-size="72" height="80">Another<a rel="noreferrer noopener" href="; target="_blank"> Pfizer press release</a> posted February 25, 2021 proposes to produce variations of the vaccine to adjust to the changes seen in B.1.351..Another Pfizer press release posted February 25, 2021 proposes to produce variations of the vaccine to adjust to the changes seen in B.1.351..

The coronavirus represents a moving target. Vaccines will only be effective for a year or even less. Until the spread of the virus has been stopped, it will continue producing variations that elude our best efforts at vaccination. The uncontrolled spread of the virus has allowed it wide latitude to evolve, especially when it infects people with weak immune systems and continues to percolate for months within compromised hosts.

Another concerning issue is the absence of neutralizing antibody in the nasal secretions of immunized people. This may allow virus to replicate in the nasopharynx (although it may not be able to invade the body). The implications of this finding are equally troubling. It is possible that immunized people may asymptomatically carry virus in the nasal cavity and allow it to spread to others.

The answer to this conundrum may be found by challenging immunized people with live virus in the nose– how will their bodies respond and how long will they carry replicating virus? We need to know this, and the only way to find out is to look at the responses of immunized people to exposure. Perhaps testing all immunized people to see if they ever carry the virus in the nose will help– although very large numbers of subjects will be needed to determine what happens under natural conditions.

(SARS-COV-2 EM photo courtesy NIAID)

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