Upalsecovatein

This study aims to investigate humoral immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and assess the impact of booster vaccines. We recruited individuals scheduled to receive either the first (original formula) or the second (bivalent) booster following the initial two-dose SARS-CoV-2 vaccination. We tested for IgG antibodies targeting the spike protein receptor-binding domain (RBD), S1, S2, and nucleocapsid protein, as well as for neutralizing antibodies against Omicron BA.2, before and 14–28 days after receiving the boosters. One year after receiving the initial series of vaccinations, all participants maintained anti-RBD/S1 antibodies. However, levels were lower in individuals who were vaccinated only compared to those who had both vaccination and prior infection (hybrid immunity). Participants with hybrid immunity also showed higher retention of neutralizing antibodies (93% compared to 24% in vaccine-only individuals). Even before receiving any booster shots, participants with hybrid immunity had antibody levels similar to those of vaccine-only individuals after their first booster. After receiving booster shots, antibody levels at 14–28 days were similar regardless of the number of boosters or the type of immunity. About 1 year after the first booster, all participants maintained neutralizing antibodies, and vaccine-only individuals retained about 10 times higher levels of binding antibodies than those without a booster. Humoral immunity varies widely among individuals, and vaccination planning should consider both vaccination and infection history. Boosters are beneficial for increasing antibody levels to ensure sufficient protection against infection and helping bridge the immunity gap between vaccine-only and hybrid immunity.

As we move into the era of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine boosters and shifting from pandemic to endemic, the landscape has changed for both the circulating SARS-CoV-2 variants and population immunity. Even though recent waves of infection have been clinically milder than earlier variants due to the high levels of population immunity and the properties of the Omicron subvariants, vaccination remains crucial for managing COVID-19 in the post-pandemic era. Our study unveils significant variations in the retention of anti-SARS-CoV-2 binding antibody profiles and neutralizing antibody levels 1 year after the primary and the first booster mRNA vaccination. It adds new information regarding how boosters change antibody levels and durability in individuals with hybrid (vaccination plus infection) or vaccine-only (never-infected) immunity. The findings can shed light on future vaccination planning.

Inactivated whole-virus vaccination elicits immune responses to both SARS-CoV-2 nucleocapsid (N) and spike (S) proteins, like natural infections. A heterologous Ad26.COV2.S booster given at two different intervals after primary BBIBP-CorV vaccination was safe and immunogenic at days 28 and 84, with higher immune responses observed after the longer pre-boost interval. We describe booster-specific and hybrid immune responses over 1 year.

This open-label phase 1/2 study was conducted in healthy Thai adults aged ≥ 18 years who had completed primary BBIBP-CorV primary vaccination between 90-240 (Arm A1; n = 361) or 45-75 days (Arm A2; n = 104) before enrolment. All received an Ad26.COV2.S booster. We measured anti-S and anti-N IgG antibodies by Elecsys®, neutralizing antibodies by SARS-CoV-2 pseudovirus neutralization assay, and T-cell responses by quantitative interferon (IFN)-γ release assay. Immune responses were evaluated in the baseline-seronegative population (pre-booster anti-N < 1.4 U/mL; n = 241) that included the booster-effect subgroup (anti-N < 1.4 U/mL at each visit) and the hybrid-immunity subgroup (anti-N ≥ 1.4 U/mL and/or SARS-CoV-2 infection, irrespective of receiving non-study COVID-19 boosters).

In Arm A1 of the booster-effect subgroup, anti-S GMCs were 131-fold higher than baseline at day 336; neutralizing responses against ancestral SARS-CoV-2 were 5-fold higher than baseline at day 168; 4-fold against Omicron BA.2 at day 84. IFN-γ remained approximately 4-fold higher than baseline at days 168 and 336 in 18-59-year-olds. Booster-specific responses trended lower in Arm A2. In the hybrid-immunity subgroup at day 336, anti-S GMCs in A1 were 517-fold higher than baseline; neutralizing responses against ancestral SARS-CoV-2 and Omicron BA.2 were 28- and 31-fold higher, respectively, and IFN-γ was approximately 14-fold higher in 18-59-year-olds at day 336. Durable immune responses trended lower in ≥ 60-year-olds.

A heterologous Ad26.COV2.S booster after primary BBIBP-CorV vaccination induced booster-specific immune responses detectable up to 1 year that were higher in participants with hybrid immunity.

NCT05109559.