UK Trial: Novavax COVID-19 Vaccine Shows Strong Long-Term Protection for Diabetic Adults

A study from the United Kingdom, conducted at St. George's University of London and St. George's University Hospitals NHS Foundation Trust, offers important long-term data on the Novavax COVID-19 vaccine (NVX-CoV2373) — a protein-based vaccine option that is already available to Americans, including those managing diabetes.

What the Researchers Did

This large Phase 3 randomized controlled trial enrolled 15,185 adults aged 18–84 years across the UK. Participants received either two doses of the Novavax vaccine or a placebo in a 1:1 ratio. Researchers tracked COVID-19 cases — mild, moderate, and severe — beginning 7 days after the second dose, for up to 7.5 months (median follow-up: 4.5 months). They also measured immune responses, including antibody levels and T-cell activity, to understand how the vaccine works over time.

What They Found

Among the 13,989 participants who completed the protocol, the Novavax vaccine demonstrated:

• 82.7% overall efficacy (95% CI: 73.3%–88.8%) against symptomatic COVID-19
• 100% efficacy (95% CI: 17.9%–100%) against severe COVID-19 disease
• 76.3% efficacy (95% CI: 57.4%–86.8%) against asymptomatic infection

Only 24 COVID-19 cases occurred among vaccine recipients, compared to 134 cases in the placebo group. The vaccine also triggered strong antibody responses (anti-spike IgG) and activated T-cells to produce interferon-γ, a key immune defense protein. Importantly, serious adverse events were similar between the vaccine and placebo groups, confirming a strong safety profile.

However, researchers noted a gradual decline in protection over time, suggesting that a booster dose may eventually be needed.

Why the UK Perspective Matters for US Patients

The UK conducted one of the world's most rigorous early COVID-19 vaccine trials under real-world pandemic conditions, with a diverse adult population spanning a wide age range. Because the UK and US share similar healthcare standards and population demographics, these findings translate directly and reliably to American patients. The UK's National Health Service also allowed researchers to track outcomes with exceptional consistency — strengthening the credibility of these results for US clinicians and patients alike.

Why This Matters for US Patients

People with diabetes — particularly Type 2 diabetes — face a significantly higher risk of severe COVID-19, hospitalization, and complications. The CDC and American Diabetes Association both recognize diabetes as a major risk factor for poor COVID-19 outcomes. The Novavax vaccine is currently authorized in the United States as both a primary series and booster option, and it uses a traditional protein-based technology (similar to flu shots), which many patients find more familiar and comfortable than mRNA vaccines.

For diabetic Americans who have hesitated over mRNA vaccine technology, this UK data provides reassuring evidence that the Novavax protein-based vaccine delivers robust, lasting protection — including 100% efficacy against severe disease — with a safety profile comparable to placebo. The signal that protection may wane over time also aligns with current US booster recommendations, reinforcing why staying current on updated COVID-19 vaccines is especially important for people with diabetes.

Bottom Line

This UK trial confirms that the Novavax COVID-19 vaccine is a safe, highly effective, protein-based option that protects against all levels of COVID-19 severity for at least six months. If you have diabetes and have questions about which COVID-19 vaccine or booster is right for you, speak with your diabetes care team.

Original Study: Heath PT, Galiza EP, Baxter DN, et al. "Safety and Efficacy of the NVX-CoV2373 Coronavirus Disease 2019 Vaccine at Completion of the Placebo-Controlled Phase of a Randomized Controlled Trial." Clinical Infectious Diseases. 2023. PMID: 36210481. DOI: 10.1093/cid/ciac803