Population-Based Evaluation of Vaccine Effectiveness against SARS-CoV-2 Infection, Severe Illness, and Death, Taiwan

Taiwan provided several COVID-19 vaccine platforms: mRNA (BNT162b2, mRNA-1273), adenoviral vector-based (AZD1222), and protein subunit (MVC-COV1901). After Taiwan shifted from its zero-COVID strategy in April 2022, population-based evaluation of vaccine effectiveness (VE) became possible. We conducted an observational cohort study of 21,416,151 persons to examine VE against SARS-CoV-2 infection, moderate and severe illness, and death during March 22, 2021-September 30, 2022. After adjusting for age and sex, we found that persons who completed 3 vaccine doses (2 primary, 1 booster) or received MVC-COV1901 as the primary series had the lowest hospitalization incidence (0.04-0.20 cases/100,000 person-days). We also found 95.8% VE against hospitalization for 3 doses of BNT162b2, 91.0% for MVC-COV1901, 81.8% for mRNA-1273, and 65.7% for AZD1222, which had the lowest overall VE. Our findings indicated that protein subunit vaccines provide similar protection against SARS-CoV-2---associated hospitalization as mRNA vaccines and can inform mix-and-match vaccine selection in other countries.

Safety, Tolerability, and Immunogenicity of Booster Dose with MVC-COV1901 or MVC-COV1901-Beta SARS-CoV-2 Vaccine in Adults: A Phase I, Prospective, Randomized, Open-Labeled Study

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines based on variant strains have been in use as booster doses to update immunity against circulating variants. Here we present the results of a phase one prospective, randomized, and open-labeled trial to study the safety and immunogenicity of a booster dose consisting of a subunit vaccine based on the stabilized prefusion SARS-CoV-2 spike protein, MVC-COV1901, or its Beta version, MVC-COV1901-Beta. Participants aged ≥18 and <55 years who received two or three prior doses of MVC-COV1901 vaccines were enrolled and were to receive a booster dose of either 15 mcg of MVC-COV1901, 15 mcg, or 25 mcg of MVC-COV1901-Beta in a 1:1:1 ratio. Adverse reactions after either MVC-COV1901 or MVC-COV1901-Beta booster doses after two or three doses of MVC-COV1901 were comparable and mostly mild and transient. At four weeks after the booster dose, participants with two prior doses of MVC-COV1901 had higher levels of neutralizing antibodies against ancestral SARS-CoV-2, Beta, and Omicron variants than participants with three prior doses of MVC-COV1901, regardless of the type of booster used. MVC-COV1901 and MVC-COV1901-Beta can both be effectively used as booster doses against SARS-CoV-2, including the BA.4/BA.5 Omicron variants.

Safety and immunogenicity of homologous versus heterologous booster dose with AZD1222, mRNA-1273, or MVC-COV1901 SARS-CoV-2 vaccines in adults: An observer-blinded, multi-center, phase 2 randomized trial

OBJECTIVES

To report the safety and immunogenicity profile of a protein subunit vaccine (MVC-COV1901) compared to AZD1222 and mRNA-1273 when given as a third (booster) dose to individuals who have completed different primary vaccine regimens.

METHODS

Individuals were classified according to their primary vaccine regimens, including two-dose MVC-COV1901, AZD1222, or mRNA-1273. A third dose of either half-dose MVC-COV1901, full-dose MVC-COV1901, standard-dose AZD1222, half-dose mRNA-1273 was administered in a 1:1:1:1 treatment ratio to individuals with an interval range of 84-365 days after the second dose. Endpoints included safety, humoral immunogenicity, and cell-mediated immune response on trial days 15 and 29. Exploratory endpoint included testing against variants of concern (Omicron).

RESULTS

Overall, 803 participants were randomized and boosted - 201 received half-dose MVC-COV1901, 196 received full-dose MVC-COV1901, 203 received AZD1222, and 203 received half-dose mRNA-1273. Reactogenicity was mild to moderate, and less in the MVC-COV1901 booster group. Heterologous boosting provided the best immunogenic response. Boosting with mRNA-1273 in MVC-COV1901 primed individuals induced the highest antibody titers, even against Omicron, and cell-mediated immune response.

CONCLUSIONS

Overall, MVC-COV1901 as a booster showed the best safety profiles. MVC-COV1901 as a primary series, with either homologous or heterologous booster, elicited the highest immunogenic response.

CLINICALTRIALS

gov registration NCT05197153.

An evaluation of the safety and immunogenicity of MVC-COV1901: Results of an interim analysis of a phase III, parallel group, randomized, double-blind, active-controlled immunobridging study in Paraguay

BACKGROUND

Data from previous studies of the MVC-COV1901 vaccine, a subunit vaccine against SARS-CoV-2 based on the stable prefusion spike protein (S-2P) adjuvanted with CpG 1018 adjuvant and aluminum hydroxide, suggest that the vaccine is generally safe and elicits a good immune response in healthy adults and adolescents. By comparing with AZD1222, this study adds to the findings from previous trials and further evaluates the breadth of protection offered by MVC-COV1901.

METHODS

In this phase 3, parallel group, randomized, double-blind, active-controlled trial conducted in 2 sites in Paraguay, we assigned adults aged 18-91 years in a 1:1 ratio to receive intramuscular doses of MVC-COV1901 or AZD1222 administered as scheduled in the clinical trial. Serum samples were collected on the day of vaccination and 14 days after the second dose. Primary and secondary safety and immunogenicity endpoints were assessed. In addition, other outcomes investigated were cross-reactive immunity against the Omicron strain and the induction of IgG subclasses.

RESULTS

A total of 1,030 participants underwent randomization. Safety data was derived from this set while primary immunogenicity data involved a per-protocol immunogenicity (PPI) subset including 225 participants. Among the participants, 58% are seropositive at baseline. When compared against AZD1222, MVC-COV1901 exhibited superiority in terms of neutralizing antibody titers and non-inferiority in terms of seroconversion rates. Reactogenicity was generally mild and no serious adverse event was attributable to MVC-COV1901. Both vaccines have a Th1-biased response predominated by the production of IgG1 and IgG3 subclasses. Omicron-neutralizing titers were 44.5 times lower compared to wildtype-neutralizing titers among seronegative individuals at baseline. This fold-reduction was 3.0 times among the seropositive.

CONCLUSION

Safety and immunogenicity data of MVC-COV1901 from the study in Paraguay confirm previous results. The previous infection coupled with vaccination of this vaccine may offer protection against the Omicron strain though its durability is still unknown.

Durability and Immunogenicity of Neutralizing Antibodies Response Against Omicron Variants After Three Doses of Subunit SARS-CoV-2 Vaccine MVC-COV1901: An Extension to an Open-Label, Dose-Escalation Phase 1 Study

Introduction

MVC-COV1901 is a protein subunit COVID-19 vaccine based on the stable prefusion spike protein S-2P adjuvanted with CpG 1018 and aluminum hydroxide. Interim results of a phase 2 clinical trial demonstrated favorable safety profile and immunogenicity and the vaccine has been authorized for use in Taiwan. However, waning antibody levels after immunization and variants of concern (VoC) could negatively impact vaccine-induced neutralization of virus. In this extension to the phase 1 clinical study we investigated a three-dose regimen of MVC-COV1901 for durability of antibody levels and virus neutralization capacity, including neutralization of the Omicron variant.

Methods

Forty-five healthy adults from 20 to 49 years of age were divided into three groups of 15 participants receiving two doses of either low dose (LD), medium dose (MD), or high dose (HD) of MVC-COV1901. Six months after the second dose (day 209), a third MD dose of MVC-COV1901 was administered to the LD and MD groups and a HD dose was given to the HD group. Safety was followed for up to 28 days after the booster dose by monitoring incidences of adverse events (AE). Immunogenicity and antibody persistence for up to 6 months after the booster dose were assessed by neutralizing assay with the wild-type (Wuhan) SARS-CoV-2 virus. To examine the immunogenicity of booster dose against variants, neutralizing assays were carried out with the Alpha, Beta, and Delta variant viruses and the Omicron variant pseudovirus using samples from 4 weeks after the booster dose.

Results

Adverse reactions after the booster dose were mostly mild and comparable to that of the first two doses. Compared to day 209, neutralizing antibodies were increased by 10.3–28.9 times at 4 weeks after the booster. During the 6-month follow-up after the booster, the rate of decline of neutralizing antibody level was much less than that after the second dose. Three doses of MVC-COV1901 also improved antibody-mediated neutralization of Alpha, Beta, and Delta variants as well as the Omicron variant pseudovirus.

Conclusion

Our data showed increased persistence of neutralizing antibodies and enhancement of immunogenicity against VoCs offered after a third dose of MVC-COV1901.

Trial Registration

ClinicalTrials.gov identifier NCT04487210.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-022-00652-6.

Protection of Hamsters Challenged with SARS-CoV-2 Delta Variant after Two Doses of Adjuvanted SARS-CoV-2 Stabilized Prefusion Spike Protein (S-2P) and a Single Dose of Beta Variant S-2P

SARS-CoV-2 Variants of Concern (VoCs) negatively impact the effectiveness of vaccines. In this study, we challenge hamsters with the Delta variant after two- or three-dose inoculations with SARS-CoV-2 vaccines constructed from stabilized prefusion spike proteins (S-2P) of Wuhan (W) and Beta (B) variants. Compared to three doses of W S-2P, two doses of W S-2P followed by a third dose of B S-2P induced the highest neutralizing antibody titer against live SARS-CoV-2 virus and enhanced neutralization of Omicron variant pseudovirus. Reduced lung live virus titer and pathology suggested that all vaccination regimens protect hamsters from SARS-CoV-2 Delta variant challenge.