This evidence synthesis has been compiled by members of the CITF Secretariat and does not necessarily represent the views of all CITF members.

By Mariana Bego 

Current mRNA vaccines may be a potent weapon against the most troublesome immune-evading SARS-CoV-2 variants. Studies in macaques hint that mRNA vaccines could be used as a platform to develop vaccines protecting against an array of coronaviruses. In a recent report from Qatar, people who received two doses of the Pfizer-BioNTech mRNA vaccine were 75% less likely to get infected with the variant initially described in South Africa (B.1.351) when compared to unvaccinated people. They also had  almost complete protection from severe disease caused by any variant. Likewise, the nanoparticle baculovirus vaccine from Novavax displayed significant protection in a South African trial where most of the infections are caused by the B.1.351 variant.

Key points:

  • Experimental mRNA vaccines have protected macaques against several coronaviruses.
  • Several COVID-19 vaccines are showing good efficacy in real-world conditions against SARS-CoV-2 variants, including the variant originally described in South Africa (B.1.351).
  • Although breakthrough infections were recorded, the vaccines discussed here protected against severe, critical, or fatal COVID-19 disease, with 97-100% efficacy.

Coronaviruses (CoVs) have caused several worldwide outbreaks: the severe acute respiratory syndrome (SARS), the Middle East Respiratory Syndrome (MERS), and now the SARS-CoV-2 pandemic.1 A recent article in Nature, by Saunders and colleagues describes experiments in macaques with a novel mRNA-based vaccine eliciting cross-neutralizing antibodies against bat CoVs, SARS-CoV-1, SARS-CoV-2, and SARS-CoV-2 variants B.1.1.7, P.1, and B.1.351.2 The authors suggest that current mRNA vaccines may provide some protection from future coronaviruses outbreaks and could be used as a platform to develop pan-CoV vaccines.

The mRNA vaccine from Pfizer-BioNTech has reported 95% efficacy against COVID-19 in controlled clinical trial settings.3 Efficacy was also reported to be very good in real-world conditions (over 90%) in both Israel4 and the United States5. Additional encouraging information is coming out of geographical areas with high prevalence of newer viral variants, such as Qatar.6 As of March 31, 2021, over 385,000 people in Qatar had received at least one dose of the Pfizer-BioNTech vaccine and more than 265,000 had completed the two doses. Vaccination scale-up occurred as Qatar was undergoing its second and third waves of ‘variant-driven’ SARS-CoV-2 infections. Nearly all cases sequenced in that country after March 7th were caused by either the variant originally described in South Africa (B.1.351) or in the United Kingdom (B.1.1.7). The estimated effectiveness of the vaccine against any documented infection with these variants was recorded at least 14 days after the second dose, as 89.5% for B.1.1.7 variant and 75% for B.1.351 variant. Although breakthrough infections were recorded, this did not translate to higher rates of hospitalization or death. Overall, the vaccine protected against severe, critical, or fatal disease due to infection with any SARS-CoV-2 variant (97.4% disease protection).

A recombinant SARS-CoV-2 nanoparticle baculovirus vaccine (NVX-CoV2373, Novavax) is currently under development and testing. In an ongoing randomized, placebo-controlled, phase 1–2 trial involving healthy adults, the NVX-CoV2373 vaccine was reported to be safe and generated a strong antigen-specific cellular immune response as well as neutralizing-antibodies.7 Novavax announced that their vaccine was 96.4% effective in preventing infections with the original strain of SARS-CoV-2 and 86% effective against the B.1.1.7 variant, while 100% effective at preventing severe illness.8

In a recent article in The New England Journal of Medicine, Shinde and colleagues described their early findings during the phase 2 primary efficacy and safety trial of this vaccine in South Africa when the predominant virus circulating was the B.1.351 variant.9 Over 4300 participants received at least one dose of either vaccine or placebo, of whom 30% were already seropositive for SARS-CoV-2 at baseline. Serious adverse events were rare. Among the 2684 baseline seronegative participants, 94% were HIV-negative. During the trial, 15 participants developed COVID-19 in the vaccine group versus in 29 in the placebo group (vaccine efficacy of 49.4%). Vaccine efficacy was higher among HIV-negative participants (60%). All the cases of COVID-19 were mild to moderate, except for one severe case in the placebo group. To be noted, most of the infections were caused by the B.1.351 variant, represented in 38 out of 41  sequenced isolates (92.7%).


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