Evaluating Safety and Immune Response of Janssen, Moderna, Pfizer/BNT, and Novavax COVID-19 Vaccines for Same and Mixed Boosters in Adolescents and Adults Aged 12-64 With and Without HIV in Kenya, DRC, and Rwanda

Plain-language summary

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus that emerged in the human population in Wuhan City, Hubei Province, China in December 2019. As of Jan 2022, there are over 328 million SARS-CoV-2 case worldwide and over 5.54 million deaths as a result of infection with SARS-CoV-2 (COVID-19). According to WHO Situation Report on 17 January 2022, Africa has 7 million confirmed cases with over 160, 804 deaths. The COVID-19 pandemic has caused global suffering, mortality, and severe economic pressures. There is thus a continued urgent global need to develop effective and safe vaccines and drugs to make them available at scale and equitably across all countries including in Africa. Despite the rapid successes in vaccine development and issuance of WHO Emergency Use Listings (EUL), the WHO SAGE Interim Reports and FDA Emergency Use Authorization (EUA) for COVID-19 vaccine evaluations have reported limitations on safety and efficacy data in certain populations including children and adolescents, pregnant women, and immunocompromised individuals such as those with HIV/AIDS who are at higher risk of severe COVID-19 disease. Africa is especially vulnerable in this respect given the high prevalence of HIV/AIDS in countries such as Kenya where the prevalence is over 20% in some places. The risk of recurring new waves of COVID-19 cases caused by Variants of Concern (VOC) exacerbates global public health crisis. A weak immune response to either single or two doses of primary vaccination against SARS-CoV-2 has been observed in immunocompromised population. Emerging data from observational studies consistently show waning immunity to primary vaccination for SARS-CoV-2 mutants, and a decline in vaccine effectiveness against SARS-CoV-2 infection and COVID-19 with time since primary vaccinations. These factors have led to consideration of the potential need for, and optimal timing of, booster doses for vaccinated populations. However, vaccine inequality, lack of availability of the same vaccine product used for primary vaccinations and unpredictable vaccine supply remain a challenge in LMIC. Consideration of heterologous COVID-19 vaccine to allow interchangeability (mix and match) use of vaccine products available in LMIC would therefore allow for programmatic flexibility. Based on a recent systematic review and meta-regression analysis, across the four WHO EUL COVID-19 vaccines with the most data (i.e., BNT162b2, mRNA 1273, Ad26.COV2.S and ChAdOx1-S \[recombinant\] vaccine), vaccine effectiveness against severe COVID-19 decreased by about 8% (95% confidence interval (CI): 4-15%) over a period of 6 months in all age groups. In adults above 50 years, vaccine effectiveness against severe disease decreased by about 10% (95% CI: 6 - 15%) over the same period. Vaccine effectiveness against symptomatic disease decreased by 32% (95% CI: 11 - 69%) for those above 50 years of age. For some inactivated vaccines (CoronaVac and COVID-19 vaccine BIBP), WHO has already issued the recommendation for the administration of an additional dose to those aged 60 years or older as part of the primary series to make initial immunity more robust. The FDA issued a EUA for the Janssen Ad26.COV.S1 COVID-19 vaccine for active immunization to prevent COVID-19 caused by SARS-CoV-2 in individuals 18 years of age and older. In September 2021, both the single dose and 2 dose Janssen COVID-19 vaccine regimens demonstrated high efficacy (79% protection (CI, 77%-80%) for COVID-19-related infections and 81 percent (CI, 79%-84%) for COVID-19-related hospitalizations. vs 94% (CI, 58%-100%) protection against symptomatic COVID-19 in the U.S. respectively. Furthermore, the safety profile of the vaccine remained consistent and generally well-tolerated in the 2 regimens. Finally, when a booster of the Janssen COVID-19 vaccine given 6 months after the single shot, antibody levels increased nine-fold one week after the booster and continued to climb to 12-fold higher four weeks after the booster. On June 14, 2021, Novavax reported the results of its PREVENT-19 pivotal Phase 3 trial of the NVX-CoV2373. The results showed an overall vaccine efficacy of 90.4% (95% CI: 82.9 - 94.6) in the US and Mexico. Sequenced data showed a vaccine efficacy was 93.2% (95% CI: 83.9 - 97.1) against Variants of Concern and Variants of Interest which represented 82% of cases. Studies of NVX-CoV2373 with Matrix-M adjuvant have demonstrated an acceptable safety and reactogenicity profile in adults ≥18 years of age. On December 20, 2021, the WHO issued interim recommendations and authorized under its emergency use listing (EUL) procedure, the NVX-CoV2373 COVID-19 vaccine developed by Novavax and Serum Institute of India. The pivotal phase 3 registration trial of the Moderna mRNA-1273 COVID-19 vaccine was conducted in the United States of America and involved about 30 000 participants aged 18 years or older with no known history of SARS-CoV-2 infection.

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