The purpose of this study is to compare post-vaccination reactions between the protein-based Novavax vaccine and the mNEXSPIKE mRNA-1283 vaccine. Specifically, the study aims to determine the rate of participant-reported symptoms associated with each type of vaccine.

Why is this study being conducted? Many individuals receive a flu vaccine each year, but fewer receive the COVID-19 booster, even though COVID-19 infection can be more severe. One possible reason is concern about vaccine side effects.

The goal of this study is to determine whether a different type of COVID-19 vaccine, called Novavax, causes fewer side effects than the more commonly used mRNA vaccines (such as Pfizer or Moderna) when administered as a seasonal booster.

What is Novavax? Novavax is a protein-based COVID-19 vaccine approved by the FDA. Earlier studies suggest that fewer side effects may occur with Novavax; however, not many studies have directly compared Novavax with mRNA vaccines

What is the purpose of this study? Eligible individuals who qualify for a COVID-19 booster are invited to participate. Participants will receive either the Novavax vaccine or an mRNA vaccine. After vaccination, participants will be asked to report any symptoms or side effects experienced. Collected information will help determine which vaccine may be better tolerated.

Why does this matter? By comparing participant experiences, this study aims to identify ways to improve acceptance and accessibility of COVID-19 booster vaccines. Findings may help increase public confidence in vaccination and support ongoing protection against COVID-19.

Inclusion Criteria:

Adults eligible for seasonal COVID-19 vaccine, ages 18 and older Signed informed consent form (ICF) and agree to participate in the study Prior receipt of one or more COVID-19 vaccines

Exclusion Criteria:

• If a person is experiencing a moderate or severe illness or infection (as judged by the study investigator) or has a fever (temperature of 38.0°C or higher) on the day they are supposed to participate in the study, they should not join until they are feeling better and the fever is gone.
• Anyone with a medical or mental health issue, or problems with substance use that might make taking part in the study risky
• People who have had a severe allergic reaction to COVID-19 vaccines in the past
• Those who have been diagnosed with inflammation in or around the heart after receiving a COVID-19 vaccine
• Individuals who have received any other vaccine within a week before joining the study or who plan to get a vaccine on the same day as the study or within 7 days afterward