Good news! Another UK-backed COVID-19 vaccine, developed by Novavax, proves to be a winner with a point estimate of vaccine efficacy of 89.3% and no cases of severe COVID-19 in those who received the actual vaccine. The vaccine also works against the UK and South African variants of the virus.
This vaccine is important because it is based on using a recombinant form of the spike protein produced in insect cells and not bacterial or mammalian cells, and uses a brand new adjuvant to boost the immune response.
Insect cells are interesting because they are really easy to grow and don’t necessarily require the same expensive infrastructure as other recombinant protein manufacturing platforms. This vaccine also needs very small amounts of the recombinant protein, making scale-up production easier. This new vaccine technology, similar to the RNA vaccines, will lower the entry-level for other vaccines in the future; for example, new SARS-CoV-2 variants and strains and just possibly EBV?
The UK Government has pre-purchased 60 million doses of the Novavax vaccine, which means the UK now have more than enough pre-ordered vaccine purchased for the UK’s population.
Importantly, the Coalition for Epidemic Preparedness Innovations (CEPI) funded the manufacturing of the vaccine for the phase 2b South African clinical trial (see below), which was supported in part by a $15 million grant from the Bill & Melinda Gates Foundation. This vaccine may therefore prove just as important as the Oxford-AstraZeneca vaccine for low and middle-income countries.
When historians write the history of the COVID-19 pandemic I have little doubt that Bill and Melinda Gates, as indiviudals, will be seen to have done more than any other individuals to tackle the pandemic globally. They are trying to ensure the vaccines are distributed across the world as equitably as possible. The same can’t be said for politicians in the rich world.
UK Phase 3 Results: 89.3% Efficacy
The study enrolled more than 15,000 participants between 18-84 years of age, including 27% over the age of 65. The primary endpoint of the UK Phase 3 clinical trial is based on the first occurrence of PCR-confirmed symptomatic (mild, moderate or severe) COVID-19 with onset at least 7 days after the second study vaccination in serologically negative (to SARS-CoV-2) adult participants at baseline.
The first interim analysis is based on 62 cases, of which 56 cases of COVID-19 were observed in the placebo group versus 6 cases observed in the NVX-CoV2373 group, resulting in a point estimate of vaccine efficacy of 89.3% (95% CI: 75.2 – 95.4). Of the 62 cases, 61 were mild or moderate, and 1 was severe (in placebo group).
Preliminary analysis indicates that the UK variant strain that was increasingly prevalent was detected in over 50% of the PCR-confirmed symptomatic cases (32 UK variant, 24 non-variant, 6 unknown). Based on PCR performed on strains from 56 of the 62 cases, efficacy by strain was calculated to be 95.6% against the original COVID-19 strain and 85.6% against the UK variant strain [post hoc].
The interim analysis included a preliminary review of the safety database, which showed that severe, serious, and medically attended adverse events occurred at low levels and were balanced between vaccine and placebo groups.
“These are spectacular results, and we are very pleased to have helped Novavax with the development of this vaccine. The efficacy shown against the emerging variants is also extremely encouraging. This is an incredible achievement that will ensure we can protect individuals in the UK and the rest of the world from this virus,” said Clive Dix, Chair, UK Vaccine Taskforce.
Novavax expects to share further details of the UK trial results as additional data become available. Additional analysis on both trials is ongoing and will be shared via prepublication servers as well as submitted to a peer-reviewed journal for publication. The company initiated a rolling submission to the United Kingdom’s regulatory agency, the MHRA, in mid-January.
South Africa Results: Approximately 90% of COVID-19 cases attributed to South Africa escape variant
In the South Africa Phase 2b clinical trial, 60% efficacy (95% CI: 19.9 – 80.1) for the prevention of mild, moderate and severe COVID-19 disease was observed in the 94% of the study population that was HIV-negative. Twenty-nine cases were observed in the placebo group and 15 in the vaccine group. One severe case occurred in the placebo group and all other cases were mild or moderate. The clinical trial also achieved its primary efficacy endpoint in the overall trial population, including HIV-positive and HIV-negative subjects (efficacy of 49.4%; 95% CI: 6.1 – 72.8).
This study enrolled over 4,400 patients beginning in August 2020, with COVID-19 cases counted from September through mid-January. During this time, the triple mutant variant, which contains three critical mutations in the receptor binding domain (RBD) and multiple mutations outside the RBD, was widely circulating in South Africa. Preliminary sequencing data is available for 27 of 44 COVID-19 events; of these, 92.6% (25 out of 27 cases) were the South Africa escape variant.
Importantly in this trial, approximately 1/3 of the patients enrolled (but not included in the primary analyses described above) were seropositive, demonstrating prior COVID-19 infection at baseline. Based on temporal epidemiology data in the region, the pre-trial infections are thought to have been caused by the original COVID-19 strain (i.e., non-variant), while the subsequent infections during the study were largely variant virus. These data suggest that prior infection with COVID-19 may not completely protect against subsequent infection by the South Africa escape variant, however, vaccination with NVX-CoV2373 provided significant protection.
“The 60% reduced risk against COVID-19 illness in vaccinated individuals in South Africans underscores the value of this vaccine to prevent illness from the highly worrisome variant currently circulating in South Africa, and which is spreading globally. This is the first COVID-19 vaccine for which we now have objective evidence that it protects against the variant dominating in South Africa,” says Professor Shabir Maddi, Executive Director of the Vaccines and Infectious Diseases Analytics Research Unit (VIDA) at Wits, and principal investigator in the Novavax COVID-19 vaccine trial in South Africa. “I am encouraged to see that Novavax plans to immediately begin clinical development on a vaccine specifically targeted to the variant, which together with the current vaccine is likely to form the cornerstone of the fight against COVID-19.”