Novel vaccine demonstrated a high overall vaccine efficacy for prevention of COVID-19

New clinical data published on the medRxiv* preprint server suggests a new coronavirus disease 2019 (COVID-19) vaccine may be on the horizon. The phase 3 PREVENT-19 clinical trial studied the efficacy of Novavax’s COVID-19 vaccine, NVX-CoV2373, and found it highly effective in preventing mild, moderate, and severe COVID-19 illness after full vaccination.

Study: Efficacy and Safety of NVX-CoV2373 in Adults in the United States and Mexico. Image Credit: ffikretow/ Shutterstock

The two-dose vaccine showed about 90% vaccine effectiveness. Against moderate to severe COVID-19 infection, NVX-CoV2373 was 100% effective. Individuals considered at high risk for severe infection showed a 91% protection against moderate or severe illness.

A strong performance was also observed against several severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. A 93.6% vaccine effectiveness against the Alpha variant was reported in the study.

Approval of the Novavax vaccine may help with the global distribution of COVID-19 vaccines. It has extended stability and can be stored for up to six months in a refrigerator. NVX-CoV2373 is based on a traditional protein-based formulation that may help people who are vaccine-hesitant from mRNA vaccines.

The study

Demographically diverse pool of participants recruited in the clinical trial

A total of 25,452 volunteers from the United States and Mexico were enrolled in the study. About 48.2% of participants were female, 75.9% were White, 11% were Black/African American, 6.2% were Native American/Alaska Native, and 21.5% identified as Hispanic/Latino. The median age was 47, and about 11.8% of participants were 65 years or older. About 17,312 were administered two doses of the NVX-CoV2373 vaccine, while 8,140 received a placebo.

Results show 100% vaccine efficacy against moderate-to-severe COVID-19 infection

About 77 PCR-test confirmed COVID-19 cases were reported during the trial. About 14 came from vaccinated individuals, and 63 came from the placebo group. The results indicate a 90.4% vaccine effectiveness. All vaccinated individuals with COVID-19 infections experienced mild symptoms. In contrast, all 14 moderate-to-severe COVID-19 cases were reported in the placebo group. The results suggest the Novavax vaccine is 100% effective against moderate-to-severe COVID-19 infection.

For people considered at high risk for severe COVID-19 complications, vaccine effectiveness was 91%. Except for Hispanic/Latinos, vaccine effectiveness was consistently high among racial groups. Hispanic/Latinos showed 67.3% vaccine effectiveness compared to other groups.

Novavax vaccine was more than 92% effective against variants of concern/variants of interest

The researchers used nasal swabs in all COVID-19 cases to sequence for SARS-CoV-2 variants. Whole-genome sequencing identified 61 of the 77 swab samples. Results showed 35 of COVID-19 cases originated from a variant of concern. About 88.6% of the variants of concerns were from the Alpha variant.

The Novavax vaccine was 93.6% protective against Alpha. For the others, 13 cases came from a variant of interest, and the other 13 came from neither a variant of concern nor a variant of interest.

The Novavax vaccine was 100% effective against SARS-CoV-2 strains that were neither variants of concerns nor variants of interest. Vaccine effectiveness was 92.6% against any variant of concern or variant of interest.

Mild to moderate adverse events reported after second vaccine dose

Mild to moderate side effects were observed with vaccinated individuals. The adverse events increased after the second dose. No severe safety concerns were reported after vaccination.

Vaccinated individuals were more likely to report tenderness and injection site pain after each dose. These adverse events lasted for about two days.

People were more likely to report headaches, muscle pain, fatigue, and general discomfort for about a day after the second dose. Fever was rare and occurred in less than 1% of vaccinated individuals.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
  • Dunkle LM, et al. (2021). Efficacy and Safety of NVX-CoV2373 in Adults in the United States and Mexico. medRxiv. doi:

Posted in: Medical Science News | Medical Research News | Disease/Infection News

Tags: Clinical Trial, Coronavirus, Coronavirus Disease COVID-19, Efficacy, Fatigue, Fever, Genome, Muscle, Pain, Placebo, Protein, Respiratory, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Syndrome, Vaccine

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Jocelyn Solis-Moreira

Jocelyn Solis-Moreira graduated with a Bachelor's in Integrative Neuroscience, where she then pursued graduate research looking at the long-term effects of adolescent binge drinking on the brain's neurochemistry in adulthood.

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