It is essential to know why a fully vaccinated person gets COVID-19 because of the public health implications. We want to know if the vaccine is still effective, or is there a new variant that is more infectious?
That’s the purpose of a study Predominance of antibody-resistant SARS-CoV-2 variants in vaccine breakthrough cases from the San Francisco Bay Area, California. [1] The investigators evaluated breakthrough cases and unvaccinated people infected by SARS-CoV-2 variants.
A breakthrough happens when a vaccinated person gets sick with COVID-19.
What Makes a Variant?
SARS-CoV-2 variants contain changes in their amino acid sequences. Amino acids can be replaced by another one.
For example, Leucine (L) replaced by Arginine (R) at position number 452 of the viral spike protein in the L452R mutation.
The table below shows the one-letter symbol for each amino acid.
Changes in the amino acid sequences affect the protein shape and properties of viruses. The variant can become more infectious, more deadly, resistant to antibodies or become more transmissible.
The research involved 1,373 COVID-19 cases. 125 or 9.1% of the study group are breakthrough infections.
Analysis showed that the fully vaccinated were more than likely to be infected with variants associated with decreased antibody response rather than a more infectious variant.
That means the antibodies developed after the COVID-19 vaccination was not able to stop the viruses. The viruses of the breakthrough cases have the L452R, L452Q, E484K, and F490S mutations. Those mutations made the SARS-CoV-2 unrecognizable to the antibodies that is why they were able to infect the cases.
Another thing to consider in COVID-19 infections is the viral load. Viral load is the number of SARS-CoV-2 present at the time of PCR testing.
A high viral load is the single most crucial factor that determines if someone will have severe COVID-19. [3] The higher the viral load, the worse the outcome.
Viral load weighs more than age, sex, hypertension, cardiovascular disease, diabetes, obesity and lung disease in determining disease severity. [3]
One may presume that the viral loads would be smaller in the vaccinated because of the acquired immunity but this study showed that the viral loads are the same for both vaccinated and unvaccinated.
As expected, the viral loads are higher in people that are more symptomatic.
neutralizing antibodies
Neutralizing antibodies or NAbs develop after natural infection or vaccination. NAbs prevent infection by blocking the SARS-CoV-2 from attaching to human cells. That’s important because after attachment, the virus enters the cells and begins to multiply rapidly.
Previous studies have shown that neutralizing antibodies in vaccinated people start to wane after six months for the Moderna [4] and Pfizer [5] vaccines.
In the San Francisco study, five breakthrough cases were found to have undetectable neutralizing antibodies due to immune suppression or were infected with an antibody resistant variant.
Decreasing neutralizing antibodies is significant because it can lead to another infection or worse, antibody dependent enhancement can happen.
Antibody-dependent enhancement results in worse and possibly fatal COVID-19.
Take Away Message
This study shows that breakthrough infections are mainly due to antibody resistant variants.
Symptomatic breakthrough cases can easily spread disease as well as the unvaccinated.
Any possible case of COVID-19 in both vaccinated and unvaccinated, should be diagnosed and treated early.
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Related:
- Durable Immunity from Pfizer COVID-19 Vaccine Lasts only Six Months
- Who develops a better Immunity against SARS-CoV-2? The vaccinated or the previously infected?
- C.D.C. reports on the Danger of the Pfizer COVID-19 vaccine to adolescents aged 12-17 years
- The Durability Study of the Moderna COVID-19 Vaccine is Strange and Unusual
- Five Mechanisms of Antibody-Dependent Enhancement
- What is Antibody-Dependent Enhancement, and why should you care.
- Antibody-dependent enhancement can happen to Delta Variant COVID-19
- Antibody-Dependent Enhancement in Breastfed Infants
- Antibodies to the Flu and COVID-19 Cross-React
- UK Data shows more COVID-19 ER visits and Deaths Among the Vaccinated
References:
- Servelita et al. Predominance of antibody-resistant SARS-CoV-2 variants in vaccine breakthrough cases from the San Francisco Bay Area, California.
- Motozono et al. SARS-CoV-2 spike L452R variant evades cellular immunity and increases infectivity. Cell Host Microbe. 2021 Jul 14;29(7):1124-1136.e11. doi: 10.1016/j.chom.2021.06.006. Epub 2021 Jun 15. PMID: 34171266; PMCID: PMC8205251.
- Soria et al. High SARS-CoV-2 viral load is associated with a worse clinical outcome of COVID-19 disease. Access Microbiol. 2021 Sep 21;3(9):000259. doi: 10.1099/acmi.0.000259. PMID: 34712904; PMCID: PMC8549390.
- Terpos et al. Robust Neutralizing Antibody Responses 6 Months Post Vaccination with BNT162b2: A Prospective Study in 308 Healthy Individuals. Life (Basel). 2021;11(10):1077. Published 2021 Oct 12. doi:10.3390/life11101077
- Bayartet al. Waning of IgG, Total and Neutralizing Antibodies 6 Months Post-Vaccination with BNT162b2 in Healthcare Workers. Vaccines (Basel). 2021 Sep 28;9(10):1092. doi: 10.3390/vaccines9101092. PMID: 34696200; PMCID: PMC8540417.