While inactivated COVID-19 vaccines (BBIBP-CorV) are effective, it is important to understand how long immunity lasts when a different vaccine is used as a booster. In this Phase 1/2 study in Thailand, healthy adults who had completed a primary inactivated vaccine series received an Ad26.COV2.S booster at different intervals. Researchers followed immune responses for one year, measuring antibodies against the original SARS-CoV-2 strain and the Omicron BA.2 variant, as well as T-cell responses. The booster induced immune responses that remained detectable for up to one year. Responses were generally stronger when the booster was given after a longer interval. Participants with “hybrid immunity” (vaccination plus natural infection) showed substantially higher antibody and T-cell responses than those without prior infection. Immune responses tended to be lower in adults aged 60 years and older. These findings suggest that a heterologous booster strategy can provide durable immune protection.

Read more: https://pmc.ncbi.nlm.nih.gov/articles/PMC12849096/

First Author: Sant Muangnoicharoen

Co-author: Arunee Thitithanyanont

Corresponding Author: Punnee Pitisuttithum