Washington: People infected after being vaccinated develop a greatly improved immune response to variants of SARS-CoV-2 virus that cause COVID-19, according to a laboratory study.
The research, published in Journal of the American Medical Association (JAMA), shows that a breakthrough infection generates a robust immune response against the Delta variant.
The results suggest that the immune response in such humans is likely to be highly effective against other variants as SARS-CoV-2 virus continues to mutate.
“One can not get a better immune response than this. These vaccines are very effective against serious disease,” said senior author Fikadu Tafesse, an assistant professor at Oregon Health & Science University (OHSU) in the United States.
“Our study suggests that individuals who are vaccinated and then exposed to a breakthrough infection have superimmunity,” Tafesse said.
The study showed that antibodies measured in breakthrough blood samples were both more abundant and much more effective – as much as 1,000 percent – than antibodies formed two weeks after the second dose of the Pfizer vaccine.
The results suggest that each post-vaccination exposure actually serves to strengthen the immune response to subsequent exposures even for new variants of the virus.
“I think this is about a final endgame. It does not mean we are at the end of the pandemic, but it does indicate where we are likely to land,” said study co-author Marcel Curlin, associate professor at OHSU School of Medicine.
“Once you are vaccinated and then exposed to the virus, you are likely to be reasonably well protected against future variants,” Curlin said.
The study suggests that the long-term outcome will be a phasing out of the severity of the worldwide epidemic, the researchers said.
Vaccine immunity, they said, is currently undergoing a real-world test against the new Omicron variant.
“We have not studied the Omicron variant specifically, but based on the results of this study, we would expect breakthrough infections from the Omicron variant to generate a similarly strong immune response among vaccinated humans,” Tafesse said.
The study compared blood samples collected from a total of 52 people, all employees at OHSU, who were vaccinated with the Pfizer vaccine and subsequently enrolled in the study.
A total of 26 people were identified through tests as having mild breakthrough infections after vaccination.
Among the sequence-confirmed breakthrough cases, 10 involved the highly contagious Delta variant, nine were non-Delta and seven were unknown variants.
The researchers then measured the immune response to live virus exposed to blood samples from people with breakthrough cases and compared it with the immune response to the control group.
They found that the breakthrough cases generated more antibodies at baseline, and these antibodies were significantly better at neutralizing the live virus.
The study underscores the fact that vaccination remains the key to stopping the pandemic.
“The key is to get vaccinated. You have to have a basis for protection,” Curlin added.
S-Africa remains at the lowest lockdown level despite record numbers of fourth-wave infections