According to a study, antibody levels against SARS-CoV-2, the virus that causes COVID-19, are more lasting in persons who were afflicted with the disease and subsequently had two doses of vaccine vs those who simply got immunised.
The study, which was published Monday in the Journal of the American Medical Association, followed 1,960 health care professionals in the United States who received both doses of either the Pfizer/BioNTech or Moderna vaccinations. Before the first vaccine dosage, 73 patients got a positive SARS-CoV-2 polymerase chain reaction (PCR) test result.
The 73 were divided into two groups: those who became ill 90 days or less before receiving the first vaccine dose, and those who became infected more than 90 days before receiving the first injection. Antibody levels were compared for persons with and without past SARS-CoV-2 infection at one, three, and six months after the second vaccine dose, after controlling for vaccine type, age, and sex.
The antibody levels of the two groups with past SARS-CoV-2 infection were also compared one and three months after the second dosage. S1, a protein subunit that is a component of the spikes present on the surface of SARS-CoV-2, is introduced to the body’s immune system by the two mRNA vaccines tested in the study.
The spikes allow the virus to grip onto and infect healthy cells. Immunoglobulin G antibodies, which are induced by S1 from vaccines that stimulate the immune system, neutralise virus particles, preventing or at least lowering SARS-CoV-2 infection.
“We discovered that health-care workers who had previously been infected with SARS-CoV-2 and then received two doses of mRNA vaccine — resulting in three independent exposures to the S1 spike protein — developed higher antibody levels than those who received vaccination alone,” said Diana Zhong, a fellow at Johns Hopkins University School of Medicine in the United States.
“At one month after the second vaccine dosage, the relative differences were 14% larger, 19% at three months, and 56% at six months,” Zhong said.
Adjusted antibody levels were 9% and 13% higher in study participants who had a PCR-confirmed SARS-CoV-2 infection more than 90 days before their initial immunisation than in those who had been exposed to the virus less than or equal to the 90-day mark.
According to research lead author Aaron Milstone, a professor at Johns Hopkins University School of Medicine, “a longer gap between infection and the first vaccine dosage may improve the antibody response.”
Milstone stated that more research is needed to see if enhanced post-vaccination durability in previously infected patients is due to the number of virus exposures, the interval between exposures, or the interaction between natural and vaccine-derived immunity.
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