Issue: February 2024
Fact checked byShenaz Bagha

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December 12, 2023
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Longer interval between COVID-19 vaccine doses increases antibody levels in IRD patients

Issue: February 2024
Fact checked byShenaz Bagha
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SAN DIEGO — A longer interval between the second and third SARS-CoV-2 vaccine doses results in greater antibody response in patients with inflammatory rheumatic diseases, according to data presented at ACR Convergence 2023.

“We know that extending the period between vaccinations increases the antibody levels against COVID in healthy individuals,” Axel Finckh, MD, leader of clinical research in the division of rheumatology at the University of Geneva, told attendees.

COVID-19 vaccine is unloaded by health care workers
“After adjusting for potential confounders, we found that the longer the interval between the second and third vaccination, the higher the antibody levels were,” Axel Finckh, MD, told attendees. Image: Adobe Stock

Finckh and colleagues had performed a previous study that suggested patients with inflammatory rheumatic diseases who received the mRNA-1273 COVID-19 (Moderna) vaccine formulation for their primary series had higher humoral immune responses compared with those immunized with BNT162b2 (Pfizer).

To assess whether the interval between second and third doses affects COVID-19 vaccine response, as well as compare the impacts of the mRNA-1273 or the BNT162b2 formulations on anti-SARS-CoV-2 spike IgG levels, in patients with inflammatory rheumatic diseases, the researchers recruited patients from the same Swiss cohort.

The current analysis included 344 patients with inflammatory rheumatic diseases who received a third COVID-19 vaccine dose between Aug. 13, 2012, and March 4, 2022. Participants completed an electronic questionnaire about their vaccine doses and provided blood samples for anti-S1-IgG level testing.

The cohort was 67% women, with a mean age of 52 years. Further baseline data showed that 34% of the study population had rheumatoid arthritis, while 36% had axial spondyloarthritis, 22% had psoriatic arthritis and 8% had undifferentiated arthritis. The mean interval between the second and third doses was 214 days (standard deviation, 25).

According to the researchers, the longer the interval between doses, the higher the antibody response was at 180 days following vaccination. This trend persisted after adjusting for potential confounders such as age and previous SARS-CoV-2 infection.

Specifically, prolonging the interval between second and third doses by 30 days yielded a 1.9-fold increase (95% CI, 1.2-3) in the likelihood of a higher antibody level after the third dose.

In all, 160 patients reported a SARS-CoV-2 infection after their third dose. These infections occurred between Dec. 28, 2021, and Dec. 5, 2022, which the researchers noted was when the B.1.1.529 omicron variant was circulating.

In addition, the researchers did not observe that the vaccination interval impacted the risk for testing positive up to 365 days after the third dose.

“After adjusting for potential confounders, we found that the longer the interval between the second and third vaccination, the higher the antibody levels were,” Finckh said. “This high level of antibodies did not result in less COVID-19 infection.”

Meanwhile, patients who received three doses of the mRNA-1273 vaccine were 3.3 times as likely to have higher anti-S1 levels than those who received the BNT162b2 formulation (P < .001), according to an adjusted analysis.

In addition, compared with the BNT162b2 series, a three-dose series of the mRNA-1273 vaccine reduced the likelihood of a positive SARS-CoV-2 test up to 365 days after the third dose by 36% (HR = 0.64; 95% CI, 0.46-0.89).

“The Moderna vaccine was associated with three to four times higher level of antibodies than the other vaccine in the following year,” Finckh said.