Results from Novavax phase 3 study in the UK

Simon Collins, HIV i-Base

On 30 June 2021, result from the UK sites in the Novavax phase 3 study were published in the NEJM. [1]

This was a randomised, placebo controlled study in over 15,000 participants who received two doses (21 days apart) of NVX-CoV2373 or placebo. The primary endpoint was confirmed COVID-19 occurring at least seven days after the second dose.

Baseline demographics included: 28% >65 years and 45% had coexisting illnesses.

There were 10 vs 96 infections in the active vs placebo groups respectively, showing efficacy of 89.7% (95% CI: 80.2 to 94.6). All 5 cases or severe infection were in the placebo group.

A post hoc analysis reported 86.3% (95% CI: 71.3 to 93.5) against the B.1.1.7 (or alpha) variant and 96.4% (95% CI: 73.8 to 99.5) against non-B.1.1.7 variants.

Serious adverse events were low and similar in the two groups.


It is always essential for phase 3 results to be published, though the interpretation of the results is complicated as the Alpha variant is no longer dominant in the UK.

PHE have recently published two studies (one not yet peer reviewed) reporting modest reductions in efficacy of both Pfizer and Oxford vaccines against the Delta compared to Alpha variants. [2, 3]


  1. Heath PT et al. Safety and Efficacy of NVX-CoV2373 Covid-19 Vaccine. NEJM. DOI: 10.1056/NEJMoa2107659. (30 June 2021).
  2. Lopez Bernal J et al. Effectiveness of COVID-19 vaccines against the B.1.617.2 (Delta) variant. NEJM. DOI: 10.1056/NEJMoa2108891. (21 July 2021).
  3. Stowe J et al. Vaccines highly effective against hospitalisation from Delta variant. PHE, pre-review access. (14 June 2021).

This report was first published on 5 July 2021.

Links to other websites are current at date of posting but not maintained.