Virus World

BACKGROUND

Early clinical data from studies of the NVX-CoV2373 vaccine (Novavax), a recombinant nanoparticle vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that contains the full-length spike glycoprotein of the prototype strain plus Matrix-M adjuvant, showed that the vaccine was safe and associated with a robust immune response in healthy adult participants. Additional data were needed regarding the efficacy, immunogenicity, and safety of this vaccine in a larger population.

METHODS

In this phase 3, randomized, observer-blinded, placebo-controlled trial conducted at 33 sites in the United Kingdom, we assigned adults between the ages of 18 and 84 years in a 1:1 ratio to receive two intramuscular 5-μg doses of NVX-CoV2373 or placebo administered 21 days apart. The primary efficacy end point was virologically confirmed mild, moderate, or severe SARS-CoV-2 infection with an onset at least 7 days after the second injection in participants who were serologically negative at baseline.

RESULTS

A total of 15,187 participants underwent randomization, and 14,039 were included in the per-protocol efficacy population. Of the participants, 27.9% were 65 years of age or older, and 44.6% had coexisting illnesses. Infections were reported in 10 participants in the vaccine group and in 96 in the placebo group, with a symptom onset of at least 7 days after the second injection, for a vaccine efficacy of 89.7% (95% confidence interval [CI], 80.2 to 94.6). No hospitalizations or deaths were reported among the 10 cases in the vaccine group. Five cases of severe infection were reported, all of which were in the placebo group. A post hoc analysis showed an efficacy of 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. Reactogenicity was generally mild and transient. The incidence of serious adverse events was low and similar in the two groups.

CONCLUSIONS

A two-dose regimen of the NVX-CoV2373 vaccine administered to adult participants conferred 89.7% protection against SARS-CoV-2 infection and showed high efficacy against the B.1.1.7 variant. (Funded by Novavax; EudraCT number, 2020-004123-16. opens in new tab.)

Published in NEJM (June 30, 2021):

https://doi.org/10.1056/NEJMoa2107659 

The trial shows the vaccine "may be a potential winner, but efficacy and safety studies need to continue,” one expert said. A potential Covid-19 vaccine from the biotech company Novavax showed a promising immune response in a small, early trial, but not without a high rate of mostly mild side effects. The results, published Tuesday, are the latest encouraging sign in the global effort to develop a vaccine for the novel coronavirus, which has killed nearly 700,000 people around the world. But the Novavax data, much like results recently published by Moderna and AstraZeneca, are too preliminary to draw any conclusions about how well the vaccine might protect against Covid-19, experts said. “It’s a small number of people in each arm, and the study wasn’t designed to demonstrate efficacy, which are the standard caveats for a Phase 1 trial,” said Edward Belongia, an epidemiologist and vaccine researcher at the Marshfield Clinic Research Institute in Wisconsin. “Having said that, it looks very promising — at least as promising if not more so than the other vaccines we’ve looked at.” The data were published on a preprint server, meaning they have not yet been peer-reviewed.

Novavax enrolled about 130 healthy volunteers in its trial and gave them either a placebo or one of four escalating doses of its vaccine. Everyone who received the vaccine developed neutralizing antibodies against SARS-CoV-2, which may help prevent infection. The best responses came from volunteers who received two injections of Novavax’s vaccine three weeks apart, plus an adjuvant meant to boost its effects. After 35 days, those participants had neutralizing antibody levels that, on average, were roughly four times higher than what was seen in a group of 32 patients who had recovered from the disease. About 80% of those volunteers had side effects at the site of injection, including pain and tenderness. More than 60% had other side effects, mostly headaches, muscle pain, and fatigue. Most reactions were mild or moderate, but eight patients had side effects that were graded severe; Novavax said none required hospitalization. All of the reactions resolved after a few days, and none was life-threatening. The study, conducted in Australia, recruited a roughly even number of men and women between the ages of 18 and 59. Volunteers were about 79% white, 15% Hispanic, 13% Asian, 6% Indigenous, and 2% Black. The median age was 31....

Preprint of the study available at medRxiv (August 4, 2020):

https://www.medrxiv.org/content/10.1101/2020.08.05.20168435v1

Background The emergence of severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) variants threatens progress toward control of the Covid-19 pandemic. Evaluation of Covid-19 vaccine efficacy against SARS-CoV-2 variants is urgently needed to inform vaccine development and use.

Methods In this phase 2a/b, multicenter, randomized, observer-blinded, placebo-controlled trial in South Africa, healthy human immunodeficiency virus (HIV)-negative adults (18 to 84 years) or medically stable people living with HIV (PLWH) (18 to 84 years) were randomized in a 1:1 ratio to receive two doses, administered 21 days apart, of either NVX-CoV2373 nanoparticle vaccine (5 micrograms recombinant spike protein with 50 micrograms Matrix-M1 adjuvant) or placebo. The primary endpoints were safety and vaccine efficacy greater than or equal to 7 days following the second dose against laboratory-confirmed symptomatic Covid-19 in previously SARS-CoV-2 uninfected participants.

Results A total of 4387 participants were randomized and dosed at least once, 2199 with NVX CoV2373 and 2188 with placebo. Approximately 30% of participants were seropositive at baseline. Among 2684 baseline seronegative participants (94% HIV negative; 6% PLWH), there were 15 and 29 predominantly mild to moderate Covid-19 cases in NVX CoV2373 and placebo recipients, respectively; vaccine efficacy was 49.4% (95% confidence interval [CI]: 6.1 to 72.8). Efficacy in HIV negative participants was 60.1% (95% CI: 19.9 to 80.1), and did not differ by baseline serostatus. Of the primary endpoint cases with available whole genome sequencing, 38 (92.7%) of 41 were the B.1.351 variant. Post-hoc vaccine efficacy against B.1.351 was 51.0% (95% CI: -0.6 to 76.2) in HIV-negative participants. Among placebo recipients, the incidence of symptomatic Covid-19 was similar in baseline seronegative vs baseline seropositive participants during the first 2 months of follow-up (5.3% vs 5.2%). Preliminary local and systemic reactogenicity were primarily mild to moderate and transient, and higher with NVX CoV2373; serious adverse events were rare in both groups.

Conclusions The NVX-CoV2373 vaccine was efficacious in preventing Covid-19, which was predominantly mild to moderate and due to the B.1.351 variant, while evidence of prior infection with the presumptive original SARS CoV-2 did not confer protection against probable B.1.351 disease. (Funded by Novavax, The Bill and Melinda Gates Foundation, and the Coalition for Epidemic Preparedness Innovations; ClinicalTrials.gov number, NCT04533399)

Preprint available in medRxiv (March 3, 2021):

https://doi.org/10.1101/2021.02.25.21252477