Novavax is a COVID-19 vaccine that uses a protein-based approach rather than the mRNA technology behind the Pfizer and Moderna shots. Sold under the brand name Nuvaxovid, it delivers a lab-made copy of the coronavirus spike protein directly into your body to trigger an immune response. In its Phase 3 clinical trial of nearly 30,000 adults, it demonstrated 90.4% efficacy at preventing symptomatic COVID-19.
How the Novavax Vaccine Works
Unlike mRNA vaccines, which give your cells genetic instructions to build the spike protein themselves, Novavax takes a more traditional route. The spike protein is manufactured outside the body using insect cells in a lab, then purified and assembled into tiny clusters called nanoparticles. When injected, these nanoparticles present the spike protein to your immune system, which learns to recognize and attack it.
The vaccine also contains an ingredient called Matrix-M, an adjuvant derived from the bark of the soapbark tree. Adjuvants are immune stimulants that amplify the body’s response, helping the vaccine produce stronger and longer-lasting protection with a smaller amount of protein. This type of technology has been used in other vaccines for decades, including some flu and hepatitis B shots, which is one reason Novavax appeals to people who prefer a more established platform.
How It Differs From mRNA Vaccines
The core difference is what gets injected. Pfizer and Moderna deliver a strand of mRNA, a set of molecular instructions that your own cells use to manufacture the spike protein temporarily. Novavax skips that step entirely and delivers the finished protein itself. Your immune system sees the protein, produces antibodies and defensive white blood cells, and builds memory to fight future infection.
This distinction matters to some people for practical or personal reasons. Novavax does not contain polyethylene glycol (PEG), a compound found in the mRNA vaccines that can cause allergic reactions in rare cases. It does contain polysorbate 80, a different stabilizer used in many existing vaccines. For anyone who had an allergic reaction to an mRNA shot, a protein-based option may be worth discussing with a provider.
Storage is another practical advantage. Novavax is kept in a standard refrigerator at 36°F to 46°F, the same conditions used for most routine vaccines. The early mRNA vaccines required ultra-cold freezers, though updated formulations have relaxed those requirements somewhat.
Efficacy in Clinical Trials
The landmark trial for Novavax was PREVENT-19, conducted in the United States and Mexico with 29,960 adult volunteers. The vaccine showed 90.4% efficacy at preventing symptomatic COVID-19 during a period when the original strain and Alpha variant were dominant. A separate Phase 3 trial in the United Kingdom confirmed that the two-dose regimen was highly effective at preventing symptomatic illness.
These numbers reflect the original formulation. Like all COVID-19 vaccines, Novavax has been updated to match circulating variants. The 2024-2025 formula targeted the JN.1 lineage, which was the dominant variant at the time. Updated formulations are expected to continue tracking whichever variant is circulating.
Who Can Get It
Nuvaxovid is FDA-approved for adults 65 and older and for people ages 12 through 64 who have at least one underlying condition that increases their risk of severe COVID-19. The most recent approval letters were issued in May and August 2025.
The current CDC guidance for the 2025-2026 season recommends one dose for people ages 12 to 64, whether or not they’ve been previously vaccinated. If you’ve had a prior COVID vaccine, you should wait at least eight weeks after your last dose. Adults 65 and older are recommended to get two doses, with the second shot six months after the first (though it can be given as early as two months later). Novavax is one of three options alongside Moderna and Pfizer for all recommended doses.
Common Side Effects
The most frequently reported side effect is soreness at the injection site. In clinical trials, about 60% of adults aged 18 to 64 experienced injection site pain after the first dose, rising to roughly 81% after the second. The pattern of side effects being more noticeable after the second dose held across all age groups and reaction types.
Fatigue and headache were the most common whole-body side effects. After the second dose, about 58% of adults aged 18 to 64 reported fatigue, and 47% reported headache. Older adults generally had milder reactions: only about 35% of those 65 and older reported fatigue after the second dose, and about 25% reported headache. Teens aged 12 to 17 had rates similar to younger adults, with roughly 58% reporting fatigue and 57% reporting headache after dose two.
These reactions are typical of vaccines in general and usually resolve within a day or two.
Rare Risks
Heart inflammation, specifically myocarditis and pericarditis, has been flagged as a rare risk with Novavax, similar to the signal seen with mRNA vaccines. In the clinical trial data, five cases of myocarditis or pericarditis were reported among Novavax recipients, with two occurring within seven days of vaccination. A risk-benefit analysis estimated roughly 5.3 excess hospitalizations or deaths from heart inflammation per 100,000 vaccinated people, weighed against an estimated 1,805 COVID cases prevented in the same group. That math favored vaccination overall, but the signal is something to be aware of, particularly for younger males who face the highest baseline risk of vaccine-associated myocarditis.
What’s in the Vaccine
The active ingredients are the recombinant spike protein (produced in insect cells) and the Matrix-M adjuvant, which contains saponins from the soapbark tree. The remaining ingredients are common vaccine components: cholesterol, phosphatidylcholine, several salt and phosphate buffers, and polysorbate 80 as a stabilizer. The manufacturing process means the vaccine may also contain trace amounts of insect cell proteins and DNA, which is standard for this production method and present in very small quantities.
Notably, Novavax does not contain mRNA, adenovirus vectors, or polyethylene glycol. For people specifically looking to avoid those components, it remains the only protein-based COVID-19 vaccine available in the United States.