Past infection of COVID-19 increases vaccine response six-fold, new study finds

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LOS ANGELES - A new study finds that those previously infected with the coronavirus may have a far greater immune response to COVID-19 vaccinations.

Researchers found that healthcare workers with a previous COVID-19 infection had six times the immune response to one dose of the Pfizer vaccine than those who hadn’t received the virus.

Between Dec. 9, 2020 and February 2021, researchers from the Universities of Sheffield, Oxford, Liverpool, Newcastle and Birmingham analyzed blood samples from 237 healthcare workers to understand their T-cell and antibody responses following vaccination from the Pfizer vaccine.

The study found that those infected with COVID-19 showed higher T-cell and antibody responses after one dose of the Pfizer vaccine, compared with people who had never had COVID-19 before and had one dose of the vaccine.

In fact, anti-spike IgG levels following a single dose in those previously infected were 6.8-fold higher in comparison to other individuals following one dose. Also, levels were still 2.9-fold higher in previously infected individuals given two doses.

In addition, the researchers discovered that the T-cell response expanded after vaccination to recognize more regions of the COVID-19 spike protein — which attacks the immune system leading to more severe illness in those individuals that were previously infected.

"Our study is one of the largest and most comprehensive accounts of the immune response to one dose of Pfizer/BioNTech vaccine comparing previously infected and infection-naïve individuals," Dr. Thuhan de Silva, a senior clinical lecturer in infectious diseases at the University of Sheffield said.

The findings suggest that the Pfizer vaccination and potentially other vaccinations provide better protection and an enhanced immune response to COVID-19 in those who were previously infected, researchers said.

It is not known how long T-cell and antibody response lasts after infection.

Other studies have echoed similar results. In a February study, researchers from the National Institutes of Health said they found evidence that people who have been previously infected by the novel coronavirus appear to be protected against reinfection, though the extent to which that protection holds up against emerging variants remains unclear.

"The data from this study suggest that people who have a positive result from a commercial antibody test appear to have substantial immunity to SARS-CoV-2, which means they may be at lower risk for future infection," said Dr. Lynne Penberthy, associate director of NCI’s Surveillance Research Program, which led the study.

However, previous studies have suggested that antibodies in COVID-19 patients decline within weeks, precluding the possibility of widespread herd immunity from natural infection.

A study published in the scientific journal "The Lancet" found that as of July 2020, fewer than 10% of U.S. adults had developed COVID-19 antibodies amid the ongoing coronavirus pandemic.