Novavax COVID-19 Vaccine Shows Lasting Protection Against Delta Variant


The biotechnology company’s recombinant spike protein-based vaccine demonstrated an efficacy of 88% after 40 days, 82% after 120 days, and 77% after 180 days during the PREVENT-19 trial.

The recombinant spike protein-based NVX-CoV2373 COVID-19 vaccine from biotechnology company Novavax demonstrated durable protection against the delta strain through 90 days, according to data published in Clinical Infectious Diseases.1 The vaccine also showed only moderate waning of efficacy over 180 days.

Novavax's NVX-CoV2373 is a recombinant spike protein-based COVID-19 vaccine / fotofabrika -

Novavax's NVX-CoV2373 is a recombinant spike protein-based COVID-19 vaccine / fotofabrika -

Although the federal public health emergency for the COVID-19 pandemic officially ended in the spring of 2023, the disease continues to be a threat due to emerging variants. According to data from the CDC, there were 13391 hospital admissions for COVID-19 in the week ending March 9, highlighting the need for ongoing strategies to reduce new infections.2

About PREVENT-19

Trial Name: A Study to Evaluate the Efficacy, Immune Response, and Safety of a COVID-19 Vaccine in Adults ≥ 18 Years With a Pediatric Expansion in Adolescents (12 to<18 Years) at Risk for SARS-CoV-2 Identifier: NCT04611802

Sponsor: Novavax

Summary: This is a phase 3, randomized, observer-blinded, placebo-controlled study to evaluate the efficacy, safety, and immunogenicity of SARS-CoV-2 rS with Matrix-M1 adjuvant in adult participants and adolescent participants. Additionally providing a Booster Dose to fully vaccinated participants. A substudy is to be conducted at selected sites to evaluate the safety and immunogenicity of a fourth dose (second booster) of NVX-CoV2373 in adults and adolescents, previously fully vaccinated and subsequently boosted with a third dose (first booster).

“Development of durable and broadly protective COVID-19 vaccines is a major focus of research,” the study authors wrote. “Protein-based vaccines have shown long lasting effects against pathogens other than SARS-CoV-2. While the durability of messenger RNA (mRNA) and vector-based COVID-19 vaccines for SARS-CoV-2 has been well characterized, less is known about protein-based vaccines.”

A team of investigators from the National Institute of Allergy and Infectious Diseases, and the Fred Hutchinson Cancer Center conducted a study to assess the vaccine efficacy and durability of NVX-CoV2373 against both pre-Delta and Delta strains of SARS-CoV-2. Data was gathered from the PREVENT-19 trial (NCT04611802), a phas 3, randomized, observer-blinded, placebo-controlled study evaluating the efficacy, safety, and immunogenicity of NVX-CoV2373.

The PREVENT-19 study included 29949 adults at an increased risk of contracting COVID-19 who received either 2 doses of NVX-CoV2373 or placebo 21 days apart. In April 2021, a blinded crossover was started in which participants who received the vaccine received placebo, and those who received placebo got the vaccine. Follow-up for the study was conducted through November 2021.

READ MORE: Vaccines to Watch in 2024

Investigators found that 2 doses of NVX-CoV2373 had an initial efficacy of 89% against pre-Delta variants, with an 87% efficacy after 90 days. Against the Delta strain, the vaccine had an efficacy of 88% after 40 days, 82% after 120 days, and 77% after 180 days. This demonstrates a modest waning of p<0.01 from day 40 to day 120. Additionally, sensitivity analysis showed the vaccine’s efficacy at 120 days ranged from 66% to 89%.

In a subgroup analysis defined by age, sex, and pre-existing conditions, the vaccine’s efficacy was similar across subgroups for pre-Delta variants. However, the vaccine showed a stronger response against the Delta variant in men 50 years of age or older and those with pre-existing conditions.

“While comparison of durability of protective efficacy of vaccines is difficult to assess due to differences in study design, endpoints, strains, and duration of follow-up, qualitatively NVX-CoV2373 aligns with the other vaccines with constant vaccine efficacy against pre-Delta strains through 3 months and waning against Delta over 5 months,” the authors wrote.

Study limitations include the study’s blinded crossover nature, the restriction to SARS-CoV-2 naïve individuals, the restriction to pre-Omicron strains, and the relatively short follow-up for pre-Delta. The authors noted that future studies should consider using a licensed vaccine control to help maintain blinding.

“While our follow-up is shorter and sample size smaller compared to other vaccines, this analysis suggests that for the period of follow-up studied here, NVX-COV2373 has a durability profile similar to the mRNA and vector-based vaccines for pre-Delta and Delta COVID-19,” the authors concluded. “Heterologous boosting with different vaccine platforms may improve durability and studies to evaluate heterologous boosting would provide useful data to inform vaccine recommendations.”

READ MORE: Immunization Resource Center

1. Follmann D, Mateja A, Fay MP, et al. Durability of Protection Against COVID-19 Through the Delta Surge for the NVX-CoV2373 Vaccine, Clinical Infectious Diseases, 2024; ciae081,
2. COVID Data Tracker. Report. CDC. March 18, 2024. Accessed March 19, 2024.
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