Two new platform vaccines against COVID-19 report phase 3 results

Simon Collins, HIV i-Base

Results from two large randomised phase 3 international studies of two COVID-19 vaccines developed on new platforms were just published in the NEJM, together with an editorial supporting research for these and additional options.

Efficacy results from the ZF2001 vaccine, which is based on the receptor-binding domain with aluminum hydroxide as an adjuvant, was studied in Uzbekistan, Indonesia, Pakistan, and Ecuador. This vaccine was given as three doses, 30 days apart. [1]

Compared to placebo, symptomatic COVID-19 was reduced by about 75% and severe infection by 87% (6 vs 43 cases), over 6 months follow-up.

The second study involved a recombinant plant-based adjuvanted vaccine, given as two intramuscular injections, 30 days apart, at 85 sites in Argentina, Brazil, Canada, Mexico, the UK, and the US.

Symptomatic infection was reduced by 70% and moderate-to-severe disease by 79%, with no severe cases in the vaccine arm.

Limitations for both studies are that they were conducted before Omicron became the dominant variant and participants were generally younger adults at low risk of severe COVID-19.

The editorial comment reports that out of almost 350 vaccine candidates in development, 31 are now approved for widespread use, using five different vaccine platforms. It also supports continued research, for compounds with formulation or efficacy benefits over the currently available vaccines.

Although it notes optimistically that by mid 2022 vaccine supply should not be a limiting factor for global coverage, there is still dramatically inequitable access and this will continue for much longer. In many low income countries, less than 10% of the population is fully vaccinated.


  1. Dai L et al. Efficacy and Safety of the RBD-Dimer–Based Covid-19 Vaccine ZF2001 in Adults. NEJM. DOI: 10.1056/NEJMoa2202261. (4 May 20-22).
  2. Hager KJ et al. Efficacy and Safety of a Recombinant Plant-Based Adjuvanted Covid-19 Vaccine. NEJM. DOI: 10.1056/NEJMoa2201300. (4 May 20-22).
  3. Nohnek H and Wilder-Smith A. Does the World Still Need New Covid-19 Vaccines? NEJM. DOI: 10.1056/NEJMe2204695. (4 May 20-22).
  4. Reuters COVID-19 vaccination tracker.



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