COVID-19 Antibody Study Demonstrates Importance of Second Vaccine Dose, Updates to Vaccine


A study profiling the antibodies present in the saliva of individuals vaccinated against COVID-19 found that patients who had received their second dose had significantly increased antibody production and protection provided by the vaccine compared to those who had received only 1 dose. Vaccinated individuals overall had large amounts of antibodies present compared to infected individuals, suggesting that vaccination both protects against becoming infected and reduces the likelihood of transmitting the virus to others, according to the study, presented at the European Congress of Clinical Microbiology & Infectious Diseases.

The investigators adapted a previously developed assay for measuring the antibodies present against SARS-CoV-2 and other coronaviruses in the blood to include targets from variants of concern and specifically examine neutralizing antibodies. Samples were collected from 23 vaccinated individuals between 26 and 58 years of age who had been given both the first and second doses of the Pfizer BioNTech vaccine, 35 infected blood donors between 40 and 78 years of age, 27 infected saliva donors between 25 and 58 years of age, and 49 non-infected saliva donors between 25 and 38 years of age. Blood and saliva samples from before the beginning of the pandemic were also sourced as a control group.

Vaccinated individuals had a substantial increase in antibodies produced and protection offered by vaccination. At the time the study was conducted, the the alpha and beta variants were the SARS-CoV-2 variants of concern, so the investigators examined whether the protection offered against these variants by vaccination was similar to that offered against the wild-type virus.

Although there was no significant reduction in effectiveness against the alpha variant, there was a substantial reduction in neutralizing antibodies when tested against the beta variant. According to the investigators, this indicates the importance of updating vaccines to offer maximum protections against new and emerging strains of the SARS-CoV-2 virus.

“Two further questions remain however with regards to vaccination,” said Nicole Schneiderhan-Marra, PhD, in a press release. “Firstly, what protection is offered by the current vaccines against the delta and any other variants that arise in the future, and secondly, how long does protection offered by the current vaccines last and will you need a booster shot to not only increase protection generally, but to also offer protection against new variants?”

As the delta variant becomes the dominant strain globally, the investigators have further developed their assays to include more targets from variants of concern. These include the delta and gamma variants, as well as other variants of interest (eta, iota, zeta, theta, kappa and epsilon) and further interesting strains, such as the mink mutation uncovered last year. The researchers continue to work on additional studies to examine how vaccine protection evolves over the course of the year and how neutralizing antibodies differ between vaccines.


Study of antibodies produced in saliva after Pfizer COVID vaccine shows both importance of second vaccine dose and updating vaccines to combat new variants of concern [news release]. EurekAlert; July 9, 2021. Accessed July 12, 2021.

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