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Immunogenicity and Safety in Healthy Adults of Full-Dose Versus Half Doses of COVID-19 Vaccine (ChAdOx1-S or BNT162b2) or Full-Dose CoronaVac Administered as a Booster Dose after Priming with Coronavac: A Randomized, Observer-Blinded, Controlled Trial Conducted in Indonesia
24 Pages Posted: 9 Aug 2022
More...Abstract
Background: Although inactivated COVID-19 vaccines effectively prevent mortality, their effectiveness for preventing infection or severe illness is known to diminish Here we aimed to evaluate the immunogenicity and safety of three potential booster vaccines administered as a homologous booster or full- or half-dose heterologous boosters among individuals primed with CoronaVac.
Methods: We conducted an observer-blind, randomized study of healthy Indonesian adults aged ≥18 years who had previously received two doses of CoronaVac within 3–<6 months or 6–9 months. Participants received a homologous booster with full-dose CoronaVac or heterologous boosters with ChAdOx1-S or BNT162b2 in full or half-dose. The primary outcome was to evaluate the seroconversion rate and geometric mean titres (GMTs) of IgG anti S-RBD 28 days after the booster in the per-protocol population. The secondary outcome was to evaluate the reactogenicity within 28 days after the booster.
Findings: Healthy adults (n = 960) were enrolled. Twenty-eight days post-booster, combining early and late booster groups, seroconversion rates were highest for BNT162b2 (97·8% and 92·0% for full and half-dose), followed by ChAdOx1-S (87·9% and 81·5% for full and half-dose) and CoronaVac (41·3% to 66·3%). All booster groups achieved 100% seropositivity 28 days after boosting. Participants in the 6–9-months priming group had higher increases in GMT values compared with participants in the 3–<6-month priming group. For participants primed within 6–9 months before booster, GMT values 28 days post-booster were highest for BNT162b2 (19999·84 and 17017·62 for full and half-dose), followed by ChAdOx1-S (11258 and 7853·04 for full and half-dose) and CoronaVac (1440·55).No serious adverse events associated with the vaccines. Within the heterologous booster group, the AERs in half-dose were lower compared with full-dose.
Interpretation: GMT values between participants in the 6–9 months priming group and the 3–<6 months priming group before the booster dose and between half dose and full dose groups 28 days post boster were not significantly different. Heterologous half- and full-dose vaccines as third doses resulted in more robust immune responses and better tolerated than homologous full-dose vaccines, therefore heterologous booster with half-dose BNT162b2 or ChAdOx1-S may be considered after 6–9 months of two doses of primary vaccine.
Trial Registration Information: The trial is registered at the Indonesia Clinical Research Registry (ina-registry.org), number INA- GO0HLGB. INA-GO0HLGB registered at https://ina-registry.org/index.php.
Funding: Ministry of Health, Republic of Indonesia
Declaration of Interest: PM is employed by the NIHRD. CBK, SRH, and JS are members of the Indonesian Technical Advisory Group on Immunization. All other authors declare no competing interests.
Ethical Approval: The Health Research Ethics Committee of National Institute of Health Research and Development (Ethical approval No.:LB.02.01/2/KE.672/2021) and the National Agency of Drug and Food Control of Indonesia (No.RG.01.06.1.3.11.21.61) approved this study.
Keywords: BNT162b2, Booster Vaccines, ChAdOx1-S, CoronaVac, COVID-19
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