Novavax COVID-19 Vaccine Less Likely to Cause Side Effects

Early last month, the pharmaceutical company Novavax shared that its two-dose COVID-19 vaccine was more than 90% effective at preventing COVID-19.

But experts have pointed to an additional interesting tidbit in the research: This new vaccine may cause fewer side effects than those currently available in the U.S.

Based on their data, the Novavax vaccine has a significantly lower rate of side effects compared to the Pfizer-BioNTech and Moderna vaccines. The symptoms commonly reported were similar to those already associated with COVID-19 vaccines like fatigue, headache, and muscle pain.

The company plans to file for U.S. Food and Drug Administration (FDA) approval. As vaccination rates stall nationwide, an additional vaccine like Novavax may seem unnecessary. But the possibility for fewer side effects and the use of reliable, trusted vaccine technology may work to convince those who remain unvaccinated to get their shot.

Fewer Side Effects May Encourage People to Get Vaccinated

Vaccine side effects can be an important factor affecting whether people get the jab.

According to the Kaiser Family Foundation, nearly half of unvaccinated adults worry about missing work if the vaccine's side effects make them feel sick for a day or more.

“Lower rates of vaccine side effects are important, in particular for adults who are concerned about lost wages or unscheduled time away from work,” Tanjala Purnell, PhD, assistant professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, tells Verywell. “On average, hourly-wage workers often earn less overall income as compared with salaried workers. Therefore, these clinical trial results may be especially appealing to people who have concerns about loss of income due to sick days or potential time away from work due to vaccine side effects and/or complications.”

If a vaccine like Novavax that causes fewer or less severe side effects becomes available, vaccination rates may increase among people in lower-income communities who can't afford to miss a day’s worth of pay. According to recent Census Bureau data, more than half of unvaccinated Americans live in households that make less than $50,000 annually.

“For example, an adult who is employed in an hourly-wage job may have less schedule flexibility and less job security than a person who is employed in a salaried position,” Purnell says. “Because of our current system of employer-based health insurance in the U.S., concerns about job security may also lead to concerns about disruptions in access to healthcare, in the event of job loss.”

The Difference Between Novavax and mRNA Vaccines

But what's behind this difference in side effects? It may due to the vaccine mechanisms at work.

The Pfizer-BioNTech and Moderna mRNA vaccines and the Novavax protein-based subunit vaccine were developed using different technology.

Subunit Vaccines

Novavax was developed using protein-based, subunit technology.

Subunit vaccines do not include any live components, containing only the specific parts of a viral or bacterial pathogen. These parts—subunits—are what the immune system needs to be exposed to so it can recognize them and develop a protective response.

“We have experience with this well-established technology and these vaccines are relatively very stable,” Inci Yildirim, MD, PhD, vaccinologist and pediatric infectious diseases specialist at Yale Medicine and associate professor of pediatrics and global health at the Yale School of Medicine, tells Verywell. “They are also relatively cheap and easy to produce. There is no live virus or bacterium in these vaccines, so certain groups such as individuals with immunocompromising disease can receive these vaccines.” 

Subunit vaccines are reliable and familiar—they have been around for many years. This technology is behind many of the routine childhood vaccinations for whooping cough, diphtheria, tetanus, and hepatitis B. They are also more stable and easier to store, unlike mRNA vaccines that require ultra-cold conditions for distribution. 

“There is a huge experience behind this technology,” Yildirim says. “Some people may find this appealing, and we may have more people getting vaccinated. The subunits included in the vaccine are necessary to elicit a protective immune response, but they are not live, or they are not whole viruses and cannot cause disease in the vaccine recipient.”

New mRNA Technology

The mRNA COVID-19 vaccines don’t use a weakened or inactivated virus to trigger an immune response either. They both use a new type of vaccine that teaches the cells to make a spike protein so the immune system can build a response against it.

Examining the specific parts of a viral or bacterial pathogen to include in a subunit vaccine is a tedious process. But that process is much easier when making mRNA vaccines.

“Determining the best antigen to include in the vaccine takes time and it will take longer to change this antigen if needed,” Yildirim says. “This will take much less time with mRNA vaccines since once the genomic target is identified, mRNA signature can be quickly and easily edited, and a new version of the vaccine can be manufactured. We have started our clinical trials with NIH/Moderna mRNA vaccine against SARS-CoV-2 within two months after the genome of the virus was sequenced.”

Aside from their technology, mRNA and subunit vaccines also differ in the immune response they evoke in the body.

“Subunit vaccines are expected to trigger only antibody-mediated immune responses,” Yildirim says. “mRNA vaccines against SARS-CoV-2 have been shown to induce B cell and T cell responses.”

This, however, doesn't drastically change efficacy rates.

“The overall efficacy of these three vaccines is similar, ranging between around 90% to 95%,” Yildirim adds. “They all have 100% efficacy for severe COVID-19 disease.”

Novavax Approval Could Still Help

It remains to be seen whether this report of fewer side effects holds up in a real-world setting.

But whether the Novavax vaccine is less likely to cause side effects or not, having a potential fourth COVID-19 vaccine in the U.S. is still beneficial.

With the approval of Novavax, healthcare providers and individuals would have more options to choose from, which may increase national and global demand.

“It is certainly important for us to have access to several vaccines that are effective against COVID-19,” Purnell says. “Globally, we continue to learn about new variants of the COVID-19 virus, and we are still learning more about long-term vaccine effectiveness over time. If we need additional booster shots in the future, it will be important for us to have an appropriate vaccine supply here in the U.S.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.