Assessment on anti-SARS-CoV-2 receptor-binding domain antibodies among CoronaVac-vaccinated Indonesian adults

The Improvement of Adaptive Immune Responses towards COVID-19 Following Diphtheria-Tetanus-Pertussis and SARS-CoV-2 Vaccinations in Indonesian Children: Exploring the Roles of Heterologous Immunity

BACKGROUND

Routine childhood vaccination, e.g., for diphtheria, tetanus, and pertussis (DTP), might provide additional protection against SARS-CoV-2 infection. This concept of heterologous immunity was explored in healthy children receiving both DTP and inactivated SARS-CoV-2 vaccines.

METHODS

A cross-sectional study was performed on 154 healthy children aged 6-8 years old in Jakarta, Indonesia. Their vaccination status for the DTP (including a diphtheria-tetanus booster vaccine at 5 years old) and CoronaVac (from 6 years old) vaccines were recorded. Peripheral blood samples were collected from all participants, in which anti-diphtheria toxoid IgG and anti-SARS-CoV-2 S-RBD antibodies and T cell-derived IFN-γ were measured.

RESULTS

The study participants with complete DTP vaccination had significantly higher titers of anti-diphtheria toxoid IgG than the ones without (median = 0.9349 versus 0.2113 IU/mL; p < 0.0001). Upon stratification based on DTP and CoronaVac vaccination statuses, the participants with complete DTP and CoronaVac vaccinations had the highest titer of anti-SARS-CoV-2 S-RBD antibodies (median = 1196 U/mL) and the highest concentration of SARS-CoV-2-specific T cell-derived IFN-γ (median = 560.9 mIU/mL) among all the groups.

CONCLUSIONS

Healthy children aged 6-8 years old with complete DTP and CoronaVac vaccinations exhibited stronger SARS-CoV-2-specific T cell immune responses. This might suggest an additional benefit of routine childhood vaccination in generating protection against novel pathogens, presumably via heterologous immunity.

S-RBD Antibody Titers Following the First and Second Doses of Inactivated SARS-CoV-2 Vaccination (CoronaVac) in Native Participants: A Prospective Cohort Study in Bali, Indonesia

Background: Vaccination has been recognized as an additional option, besides the health protocols practices to control the coronavirus disease 2019 (COVID-19) pandemic, especially with the unknown specific treatment for the disease. This study sought to evaluate the immunogenicity of CoronaVac among the general population in Bali province, a popular tourist spot in Indonesia. Methods: As many as 422 volunteers were recruited from the three vaccination centers, of which 230 volunteers were seronegative and included in the study. CoronaVac was used as vaccine with dose of 0.5 mL or 3 µg at each administration. Blood samples were drawn before vaccination, 21 days after the first dose, and 56 days after second dose, where the interval between the first and second dose vaccination was 28 days. Vaccine immunogenicity was evaluated by the anti-spike receptor-binding domain (anti-S-RBD) IgG titer which was measured using the electrochemiluminescence immunoassay technique. Results: The mean anti-S-RBD levels at 21 days after first dose, and 21 days after the second dose of vaccination are 25.25 ± 59.74 U/mL and 138.77 ± 90.93 U/mL, respectively. The result of the Friedman test was p <0.001 which means that there are significant differences in anti-S-RBD levels between 21 days after first dose and 21 days after second vaccination. Post hoc analysis with the Wilcoxon test also showed significant difference among the three-testing point (p < 0.001). The seroconversion rate from the first dose of CoronaVac was 69.7% and it increased to 99.4% (171/172) on after the second dose. Conclusion: Although the protective level was not totally reached on the first vaccination, the immunogenicity was considered rapid 3 weeks after the first vaccination.

SARS-CoV-2 Breakthrough Infection after mRNA-1273 Booster among CoronaVac-Vaccinated Healthcare Workers

It remains unknown whether the Indonesian healthcare workers (HCWs) who had received two doses of CoronaVac vaccine and one dose of mRNA-1273 booster could be protected during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron wave. In total, 125 infection-naïve and 10 previously infected HCWs were recruited. The mRNA-1273 booster substantially increased titer of anti-SARS-CoV-2 spike protein receptor-binding domain antibodies. However, the monitoring revealed that 34 out of 125 infection-naïve (27.2%) and 3 out of 10 previously infected HCWs (30.0%) were infected during the Omicron wave. All infected HCWs were either asymptomatic or having mild coronavirus disease 2019 (COVID-19) and subsequently fully recovered, supporting the heterologous prime-boost strategy against COVID-19.

Heterologous prime-boost with the mRNA-1273 vaccine among CoronaVac-vaccinated healthcare workers in Indonesia

Purpose

This study was performed to investigate humoral immune response and adverse events upon the heterologous prime-boost with a single dose of the mRNA-1273 vaccine among fully CoronaVac-vaccinated, infection-naïve healthcare workers in Indonesia.

Materials and Methods

One hundred twenty-five eligible healthcare workers were recruited from one hospital for this prospective cohort study. Blood collection was conducted twice, i.e., on 7 days before and 28 days after the booster vaccination. The titer of anti-SARS-CoV-2 receptor-binding domain (RBD) antibodies was quantified accordingly. The post-vaccination adverse event was recorded for both CoronaVac and mRNA-1273 vaccinations. Any breakthrough infection was monitored during the follow-up period. Wilcoxon matched-pairs signed rank test was used to test differences between groups.

Results

A significant increase was observed in the titer of anti-SARS-CoV-2 RBD antibodies upon receiving the mRNA-1273 booster (geometric mean titers of 65.57 and 47,445 U/mL in pre- and post-booster, respectively), supporting the argument to use heterologous prime-boost vaccination to improve the protection against COVID-19 in a high-risk population. The mRNA-1273 vaccine, however, caused a higher frequency of adverse events than the CoronaVac vaccine. Nonetheless, the adverse events were considered minor medical events and temporary as all subjects were not hospitalized and fully recovered. Of note, no breakthrough infection was observed during the follow-up to 12 weeks post-booster.

Conclusion

The heterologous prime-boost vaccination of healthcare workers with a single dose of the mRNA-1273 vaccine generated a significant elevation in humoral immune response towards RBD of SARS-CoV-2 and was associated with a higher frequency, but minor and transient, adverse events.