Vaccines prepare the body’s immune system to recognize and fight off specific pathogens. The development of COVID-19 vaccines introduced various technological approaches. Among the available options, the Novavax and Pfizer-BioNTech vaccines represent two distinct methods for building immunity against the virus.
How They Work
The Novavax vaccine uses protein subunit technology. It directly delivers a purified version of the SARS-CoV-2 spike protein, the viral component that enables cell entry. These spike protein components are produced in insect cells, then extracted and purified. An adjuvant, Matrix-M™, derived from the soapbark tree, enhances the immune response, helping the immune system recognize the spike protein and generate protective antibodies and T-cells.
In contrast, the Pfizer-BioNTech vaccine employs messenger RNA (mRNA) technology. It provides genetic instructions in the form of mRNA, without containing the virus itself. Once injected, human cells take up these mRNA instructions and temporarily use them to produce the SARS-CoV-2 spike protein. The immune system then identifies this protein as foreign and mounts an immune response, creating antibodies and immune cells. After the protein is made, the mRNA instructions are broken down and eliminated from the body, without entering the cell’s nucleus or altering a person’s DNA. Neither vaccine contains live virus or can cause COVID-19.
What They Contain
Both vaccines include inactive ingredients that contribute to their stability and effectiveness. The Novavax vaccine contains the recombinant SARS-CoV-2 spike protein and the Matrix-M™ adjuvant. Other ingredients include cholesterol, phosphatidylcholine, potassium dihydrogen phosphate, potassium chloride, disodium hydrogen phosphate dihydrate, sodium chloride, disodium hydrogen phosphate heptahydrate, sodium dihydrogen phosphate monohydrate, and polysorbate 80.
The Pfizer-BioNTech vaccine’s main active ingredient is messenger ribonucleic acid (mRNA). This mRNA is encapsulated within tiny lipid nanoparticles (LNPs), which protect the fragile mRNA and facilitate its entry into human cells. Other inactive ingredients in the Pfizer formulation include sucrose, tromethamine, and tromethamine hydrochloride, which act as stabilizers and pH adjusters.
Effectiveness and Side Effects
Clinical trials for both vaccines demonstrated high efficacy in preventing symptomatic COVID-19. Pfizer-BioNTech showed approximately 95% efficacy, and Novavax reported around 90.4% in its initial trials. Both vaccines are effective in preventing severe illness, hospitalization, and death from COVID-19. Real-world data often show comparable protection against severe outcomes.
Common side effects for both Novavax and Pfizer vaccines are mild to moderate and temporary, resolving within a few days. These can include pain, redness, or swelling at the injection site. Systemic side effects like fatigue, headache, muscle pain, chills, and fever have also been reported. A rare but notable side effect associated with mRNA vaccines, including Pfizer’s, is myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart), particularly in adolescent males and young adults. While rare cases of myocarditis were observed in Novavax trials, insufficient evidence established a causal link.
Logistics and Use
Storage conditions vary significantly between the two vaccines, impacting their distribution and accessibility. The Novavax vaccine offers a logistical advantage as it can be stored at standard refrigeration temperatures, between 2°C and 8°C (36°F and 46°F), until its expiration date. This makes it easier to transport and store in various healthcare settings, including those with limited ultra-cold storage capabilities. The vaccine is provided in a ready-to-use form, requiring no dilution or mixing.
In contrast, the Pfizer-BioNTech vaccine initially required ultra-cold storage, typically between -90°C and -60°C (-130°F and -76°F), although newer formulations and increased stability have allowed for longer periods at standard refrigeration temperatures after thawing. This ultra-cold requirement posed challenges for distribution, particularly in areas without specialized freezers.
The primary series for Novavax involves two doses administered three weeks apart. For Pfizer, the primary series also consists of two doses given three weeks apart. Both vaccines have updated formulations targeting current circulating variants, and specific dosing schedules, including booster doses, vary based on age, immune status, and prior vaccination history. The Novavax vaccine is authorized for individuals 12 years of age and older, while the Pfizer vaccine is authorized for those 6 months and older. Regulatory bodies continue to update recommendations for specific age groups and conditions.