Neutralizing antibody and T cell responses against SARS-CoV-2 variants of concern following ChAdOx-1 or BNT162b2 boosting in the elderly previously immunized with CoronaVac vaccine

Evidence synthesis and pooled analysis of vaccine effectiveness for COVID-19 mRNA vaccine BNT162b2 as a heterologous booster after inactivated SARS-CoV-2 virus vaccines

Introduction of primary COVID-19 vaccination has helped reduce severe disease and death caused by SARS-CoV-2 infection. Understanding the protection conferred by heterologous booster regimens informs alternative vaccination strategies that enable programmatic resilience and can catalyze vaccine confidence and coverage. Inactivated SARS-CoV-2 vaccines are among the most widely used vaccines worldwide. This review synthesizes the available evidence identified as of May 26, 2022, on the safety, immunogenicity, and effectiveness of a heterologous BNT162b2 (Pfizer-BioNTech) mRNA vaccine booster dose after an inactivated SARS-CoV-2 vaccine primary series, to help protect against COVID-19. Evidence showed that the heterologous BNT16b2 mRNA vaccine booster enhances immunogenicity and improves vaccine effectiveness against COVID-19, and no new safety concerns were identified with heterologous inactivated primary series with mRNA booster combinations.

Comparison of Immunogenicity of Alum and MF59-Like Adjuvant Inactivated SARS-CoV-2 Vaccines Against SARS-CoV-2 Variants in Elderly Mice

The constant emergence of variants of concern (VOCs) challenges the effectiveness of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines over time. This is most concerning in clinically vulnerable groups, such as older adults. This study aimed to determine whether the novel adjuvant MF59-like adjuvant can improve cross-immunity against VOCs in aged animals. We compared the humoral and cellular immune responses of Alum and MF59-like adjuvant-formulated inactivated coronavirus disease 2019 (COVID-19) vaccines against prototype and SARS-CoV-2 variants in 18-month-old mice. Our results showed that two doses of the MF59-like adjuvant inactivated vaccines induced more robust binding and pseudo-neutralizing antibodies (Nabs) against the SARS-CoV-2 prototype and VOCs compared to the Alum-adjuvant and reduced Omicron variant escapes from Nabs in aged mice. The humoral immune responses of inactivated vaccines were much lower against VOCs than the prototype with or without adjuvants; however, T cell responses against VOCs were not affected. In addition, Alum and MF59-like adjuvanted vaccines induced Th1-biased immune responses with increased interferon-gamma and interleukin (IL)-2 secreting cells, and hardly detectable IL-4 and IL-5. Furthermore, the MF59-like adjuvant vaccine produced 1.9-2.0 times higher cross-reactive T cell responses against the SARS-CoV-2 prototype and VOCs than the Alum adjuvant. Therefore, our data have important implications for vaccine adjuvant strategies against SARS-CoV-2 VOCs in older adults.

Neutralizing antibody and T-cell responses against SARS-CoV-2 variants by heterologous CoronaVac/ChAdOx-1 vaccination in elderly subjects with chronic obstructive pulmonary disease

BACKGROUND

Data on humoral and cellular immune responses against SARS-CoV-2 after receiving heterologous CoronaVac/ChAdOx-1 (CoVac/ChAd) vaccination in subjects with chronic obstructive pulmonary disease (COPD) are still limited. Therefore, we determined the neutralizing antibody (NAb) and T-cell responses against SARS-CoV-2 wild type (WT) and variants of concern (VOCs) in COPD patients.

METHODS

The levels of NAb as well as specific CD4 and CD8 T-cell responses against SARS-CoV-2 WT and VOCs were determined in COPD patients before and after vaccination.

RESULTS

Four weeks after vaccinations, the median levels of % inhibition of NAb against SARS-CoV-2 WT, Alpha, Beta, and Delta variants were significantly higher compared to pre-vaccination. The induction of NAb against Omicron was very low compared to other variants. At four weeks after vaccination, in comparison to pre-vaccination, the increasing trend of TNF-α-, IFN-γ-, IL-4-, IL-17-, IL-10-, and FasL-producing CD4 T-cells upon stimulation with WT spike peptides were demonstrated. No difference in T-cell responses to spike peptides of Alpha, Beta, and Delta variants and their WT homologs was observed.

CONCLUSION

Heterologous CoVac/ChAd vaccine induced the production of NAb against SARS-CoV-2 WT, Alpha, Beta, and Delta variants, but low for Omicron in COPD patients. Induction of CD4 T-cell subset responses was slightly observed by this vaccine regimen.

CLINICAL TRIALS REGISTRY

This study was approved by the Clinical Trials Registry (Study ID: TCTR20210822002).

Levels and durability of neutralizing antibodies against SARS-CoV-2 Omicron and other variants after ChAdOx-1 or BNT162b2 booster in CoronaVac-primed elderly individuals

The outbreak of the SARS-CoV-2 Omicron variant raised the need for vaccine boosting. We evaluated the efficiency of the third booster vaccine, ChAdOx-1 or BNT162b2, in causing a neutralizing antibody (NAb) response and its durability against the Omicron and other variants in elderly individuals previously vaccinated with 2-dose CoronaVac inactivated vaccine. After receiving 2-dose CoronaVac, only 2.2% of subjects had NAbs against the Omicron variant above the cut-off value. Four weeks after boosting, the number of subjects who had NAb levels above the cut-off values in the ChAdOx-1 and BNT162b2 vaccine boosting groups increased to 41.7% and 54.5%, respectively. However, after 12 and 24 weeks of boosting with any vaccines, NAb levels against the Omicron variant dramatically waned. Twenty-four weeks after boosting, only 2% had high levels of NAbs against the Omicron variant. Compared to other variants, the Omicron variant was less responsive to boosting vaccines. The waning rate of NAb levels for the Omicron variant was much faster than that observed in the Alpha, Beta and Delta variants. To combat the Omicron variant, the fourth booster dose is, therefore, recommended for elderly individuals.

Monitoring of Both Humoral and Cellular Immunities Could Early Predict COVID-19 Vaccine Efficacy Against the Different SARS-CoV2 Variants

Reliable immunoassays are essential to early predict and monitor vaccine efficacy against SARS-CoV-2. The performance of an Interferon Gamma Release Assay (IGRA, QuantiFERON® SARS-CoV-2), and a current anti-spike serological test, compared to a plaque reduction neutralization test (PRNT) taken as gold standard were compared. Eighty vaccinated individuals, whose 16% had a previous history of COVID-19, were included in a longitudinal prospective study and sampled before and two to four weeks after each dose of vaccine. In non-infected patients, 2 doses were required for obtaining both positive IGRA and PRNT assays, while serology was positive after one dose. Each dose of vaccine significantly increased the humoral and cellular response. By contrast, convalescent subjects needed a single dose of vaccine to be positive on all 3 tests. Both IGRA and current serology assay were found predictive of a positive titer of neutralizing antibodies that is correlated with vaccine protection. Patients over 65 or 80 years old had a significantly reduced response. The response tended to be better with the heterologous scheme (vs. homologous) and with the mRNA-1273 vaccine (vs. BNT162b2) in the homologous group, in patients under 55 and under 65 years old, respectively. Finally, decrease intensity or absence of IGRA response and to a less extent of anti-spike serology were also correlated to reinfection which has occurred during the follow up. In conclusion, both IGRA and current anti-spike serology assays could be used at defined thresholds to monitor the vaccine response against SARS-CoV-2 and to simply identify non-responding individuals after a complete vaccination scheme. Two available specific tests (IGRA and anti-spike antibodies) could early assess the vaccine-induced immunity against SARS-CoV-2 at the individual scale, to potentially adapt the vaccination scheme in non-responder patients.

Neutralizing Antibody and T-Cell Responses against SARS-CoV-2 Wild-Type and Variants of Concern in Chronic Obstructive Pulmonary Disease Subjects after ChAdOx-1/ChAdOx-1 Homologous Vaccination: A Preliminary Study

Data on immunogenicity of adenovirus-vectored vaccine in chronic obstructive pulmonary disease (COPD) patients is limited. Therefore, we aimed to determine the humoral and cellular immune responses after homologous ChAdOx-1 vaccination in subjects with COPD. COPD subjects and age- and sex-matched healthy elderly receiving ChAdOx-1 homologous vaccination were included. The levels of neutralizing antibodies (NAb) and specific CD4 and CD8 T-cell responses against SARS-CoV-2 wild-type (WT) and variants of concern (VOCs: Alpha, Beta, Delta, and Omicron) were measured. Eight COPD patients were matched with eight control participants. After vaccination for 4 and 12 weeks, % inhibition of NAb against Alpha, Beta, and Delta in both groups were comparable and significantly higher than baseline. The percentage inhibition of NAb at the 12th week was significantly dropped from the 4th week in each group. The NAb against the Omicron variant, however, were much lower than Alpha, Beta, Delta variants. The increasing trend in the number of CD4 T-cells producing TNF-α, IFN-γ, IL-10, and FasL upon stimulation with spike peptides of WT and VOCs was observed in COPD patients compared to the healthy group. These responses were not observed in CD8 T-cells. Homologous ChAdOx-1 vaccination could induce comparable NAb against the SARS-CoV-2 WT, Alpha, Beta, Delta, and Omicron variants between COPD and healthy elderly. The CD4 T-cell responses did not differ between COPD patients and healthy control.