- Health authorities only approve the use of COVID-19 vaccines that have gone through rigorous clinical trials.
- Scientists assess whether a vaccine is effective by checking whether participants in a trial develop the infection after having the vaccine.
- In the present study, researchers find that a person’s antibody response could serve a correlate of effectiveness, instead of whether people develop the infection.
- Using this proposed measure could speed up the regulatory approval of future vaccines.
In a new study, scientists have found that antibody levels can help indicate the effectiveness of the Moderna COVID-19 vaccine.
The research, published in the journal Science, may be the first step toward speeding up the regulatory approval process for future vaccines.
In theory, scientists could use antibody levels to identify vaccine effectiveness, rather than clinical trials to investigate how many vaccinated people develop severe COVID-19.
Vaccine development
The speed with which scientists have developed vaccines for SARS-CoV-2, the virus that causes COVID-19, is unprecedented.
Previously, vaccine development typically took 10–15 years. By contrast, the Pfizer-BioNTech vaccine received emergency regulatory approval from the Food and Drug Administration (FDA) on December 11, 2020, less than a year after scientists first identified the virus.
However, researchers are still eager to reduce the time it takes to develop future vaccines.
Scientists may do this by identifying biomarkers that can stand in for the results of clinical trials. If these biomarkers can accurately predict how effective the vaccine is, it may obviate the need to see how many people develop the infection in a clinical trial.
Speaking to Medical News Today, Prof. Florian Kern, chair in immunology at the Brighton and Sussex Medical School, in the United Kingdom, said, “If it were possible to define a laboratory endpoint — in this case an immunological marker — that can tell us if someone is protected or not, it would be easier to measure the protective effect of a vaccine quickly and compare this effect to that of other vaccines.” Prof. Kern was not involved in the new study.
Phase 3 trial data
In the study, the researchers wanted to see whether antibodies produced in response to the Moderna COVID-19 vaccine could accurately predict whether the vaccine was effective.
They did this by analyzing data from the phase 3 trials of the vaccine. The researchers were looking at the level of binding and neutralizing antibodies produced and at certain properties of these antibodies.
The team focused on these biomarkers assessed at the point of the second vaccination and 4 weeks afterward.
Antibody levels and vaccine efficacy
The researchers found a clear link between higher levels of antibodies and greater protection against symptomatic COVID-19 .
Participants with antibody levels in the top 10% had a 10 times lower risk of symptomatic COVID-19 compared with participants who had undetectable or negative antibody values. This was the case no matter which antibody biomarker the researchers focused on.
MNT spoke with Dr. Peter Gilbert, a professor in the Vaccine and Infectious Disease Division of Fred Hutchinson Cancer Research Center, in Seattle, and the corresponding author of the study.
Summarizing the findings, Dr. Gilbert explained, “Four separate tests used to measure antibody levels in the blood showed that the higher a vaccine recipient’s antibody response, the less likely [they were] to experience symptomatic COVID-19.”
“The same measurements also indicated that higher antibody responses correlated with higher estimated vaccine efficacy against symptomatic COVID-19.”
“The findings are based on data from the phase 3 COVE trial, which enrolled more than 30,000 adult volunteers and established 94.1% estimated vaccine efficacy against COVID-19 for the mRNA-1273 vaccine,” Dr. Gilbert added.
He also noted that the findings may help accelerate the approval process for future vaccines.
“Correlates of protection are surrogate markers of efficacy that can be used to reliably predict whether a vaccine will be protective, which can accelerate regulatory authorization and approval of vaccine candidates.”
“Rather than conducting large-scale clinical trials to establish vaccine efficacy, which can require tens of thousands of volunteers and can take months to years to complete, data collected from blood samples from smaller cohorts of vaccinated individuals can be evaluated using a particular test that would indicate whether a vaccine is likely to have clinical benefit in that population.”
– Dr. Peter Gilbert, corresponding author of the new study
The study authors caution that their investigation had a short follow-up period and included a relatively small number of COVID-19 cases. Also, the group did not consider the effects of booster vaccines or different variants of the virus, as these had not emerged when the trial was conducted. The trial had sampled a large and ethnically diverse number of participants for its immunogenicity measurements.
“While it may seem like an obvious finding that that more antibodies equates to higher levels of protection against COVID-19, this detailed analysis advances evidence toward establishing a correlate of protection that could be used to accelerate regulatory processes for variant-specific formulations of mRNA COVID-19 vaccines, as well as authorization of prototype mRNA COVID-19 vaccines in children,” said Dr. Gilbert.
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