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expert reaction to press release from Novavax reporting results (U.S. and Mexico data) from the PREVENT-19 Phase 3 trial of its COVID-19 vaccine candidate

A press release from Novavax states that their COVID-19 vaccine candidate demonstrates 90% overall efficacy and 100% protection against moderate and severe disease in the PREVENT-19 Phase 3 trial.

This Roundup accompanied an SMC Briefing.


Prof Paul Heath, Professor of Paediatric Infectious Diseases and Director of the Vaccine Institute, St George’s, University of London and St George’s Hospital, London, and Chief Investigator of the Novavax United Kingdom trial, said:

“These preliminary results from the large US/Mexico PREVENT-19 trial confirm the high efficacy and safety of the Novavax COVID-19 vaccine shown earlier in the year in the UK Novavax Vaccine Trial (an overall efficacy of 89%).

“The results are very reassuring and importantly show that this vaccine appears to be safe and effective in populations from a range of communities and demographic groups, and those with a range of underlying comorbidities, now (across both trials) with a total number of participants of more than 45,000.  Both the UK and US/Mexico trials used the same case definitions, and these consistent results therefore provide much confidence in the use of this vaccine for the global population.  We now await the peer-reviewed publication.  We also look forward to the results of the trial’s adolescent arm (12 to 17 years of age) which recently completed enrolment.”


Dr Peter English, Retired Consultant in Communicable Disease Control, Former Editor of Vaccines in Practice, Immediate past Chair of the BMA Public Health Medicine Committee, said:

“This is excellent news!

“The phase III trial enrolled 29,960 participants 18 years of age and older, and there were 77 cases.  It will, thus, provide robust safety data, and a fair estimate of efficacy.

“The vaccine is a much more traditional sort of vaccine than the mRNA and vector vaccines currently in use: the actual spike protein is injected, in the form of nanoparticles, instead of inserting the genetic material enabling our cells to create the spike protein.  It remains to be seen whether this will have consequences in terms of real-world effectiveness or safety; but the more different types of vaccine we have, the greater our ability will be to optimise effectiveness and safety in different groups.

“It also remains the case that producing vaccines is difficult, as the safety requirements are so important.  Any minor imperfection in the production plant can shut down production for days or weeks; so the more, different manufacturers we have producing vaccine, the more likely it is that we will have availability of vaccines.

“There is some evidence – as there is with other vaccines – that some of the variants of concern that have arisen may, to some extent, “escape” Novavax’ vaccine.  The good news is that, now the platform exists for producing this vaccine, Novavax (like other manufacturers) may soon have variant-adapted vaccines that will be as effective against the Variants of Concern as the existing vaccines are against the original strain of the SARS-CoV-2 virus.”



All our previous output on this subject can be seen at this weblink:



Declared interests

Prof Paul Heath: “Paul Heath reports grants to his Institution from Janssen, Novavax, Pfizer and Astra Zeneca.”

Dr Peter English: “No conflict of interest to declare.”

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