In a small study, people with previous COVID infection were observed to have higher antibody levels after a single dose of Pfizer vaccine compared with uninfected people after two doses.
Furthermore, there was no increase in IgG levels after the second dose among those previously infected, possibly indicating that one dose of vaccine may be sufficient for this population, reported James Moy, MD, of Rush University Medical Center in Chicago, and colleagues in a JAMA Network Open research letter.
“This study highlights the potential for recommending a single dose for previously infected individuals and may be useful for discussions surrounding vaccination strategy,” the authors wrote.
Whether to offer only a single dose of vaccine to those previously infected with COVID is a hot topic, with some experts conceding that previously infected individuals likely only need one dose, but would be challenging to implement.
Indeed, Dr Moy’s group urged performing “baseline serological testing” for previously infected individuals, but CDC and the agency’s Advisory Committee on Immunization Practices (ACIP) argued that this would be next to impossible to do for the entire country.
At a meeting in March, ACIP Chair José Romero, MD, voiced concern that the one-dose strategy would only work if individuals had sufficiently high antibody titers. If people had no or low antibodies, they may not have “enough memory B-cells to boost to levels that will be protective,” he said.
The researchers recruited adult participants at the team’s academic medical center, sorting them according toinfection status. Prior infection was established by a positive RT-PCR test and/or a positive SARS-CoV-2 antibody result. Overall, 30 participants had no evidence of infection, while 29 did.
The authors measured SARS-CoV-2 spike IgG levels at baseline and then after the first and second doses of the Pfizer vaccine among all participants.
There were no significant IgG differences between the first and second dose in previously infected individuals. Interestingly, four participants reported a previous positive COVID test via RT-PCR, but had no evidence of antibodies.
“Vaccine responses in these four participants resembled infection-naive individuals,” Moy’s group noted, adding that because this group did not develop S-protein antibodies, baseline testing should be required before forgoing a second dose.
The researchers said study limitations included the small sample size and lack of diversity of participants, as well as lack of neutralisation studies and T-cell response studies.
Source: MedPage Today
