Spikevax
Spikevax (Moderna COVID-19 vaccine) is an mRNA vaccine. It's used to prevent infection from the virus that causes COVID-19. Spikevax is FDA approved for people ages 65 years and older. It's also approved for people ages 6 months to 64 years with at least one risk factor for serious problems from COVID. This vaccine is given by a healthcare professional as an injection into the muscle. Most people only need 1 dose of the updated Spikevax booster shot for the year, except for babies who've never been vaccinated before. Side effects include pain at the injection site, muscle pain, and tiredness.
What is Spikevax?
What is Spikevax used for?
Prevention of COVID-19 infection in people 65 years of age and older
Prevention of COVID-19 infection in people between 6 months and 64 years old with at least one condition that puts them at high risk of serious problems from illness
How Spikevax works
Spikevax is an mRNA vaccine. It contains lab-made mRNA (genetic information). This piece of mRNA teaches your body to make a part of the "spike protein" found on the COVID-19 virus.
Your immune system sees this spike protein as something that doesn't belong in your body. This causes your immune system to make antibodies against the protein. These antibodies tell other immune cells to get rid of the protein from the body.
Afterwards, your immune system remembers what the COVID spike protein looks like. So if you get exposed to COVID, your immune system is ready to fight and protect you from getting very sick.
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What are the side effects of Spikevax?
Common Side Effects
- Pain at the injection site
- Feeling tired
- Headache
- Muscle pain
- Joint pain
- Chills
- Swelling or tenderness of lymph nodes in the armpit of the injected arm
Other Side Effects
- Redness or swelling at the injection site
- Reactions at the injection site that happen more than 7 days after vaccination (e.g., pain, redness, swelling)
- Fever
- Nausea or vomiting
Serious Side Effects
- Inflammation or swelling of the heart: chest pain, shortness of breath, a racing heart
- Serious allergic reaction: trouble breathing; rash; hives; swelling of the face, lips, tongue, or throat
Source: FDA
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The following side effects have also been reported
Side effects that you should report to your care team as soon as possible:
- Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
- Heart muscle inflammation—unusual weakness or fatigue, shortness of breath, chest pain, fast or irregular heartbeat, dizziness, swelling of the ankles, feet, or hands
Side effects that usually do not require medical attention (report these to your care team if they continue or are bothersome):
Pros and cons of Spikevax
Pros
Usually need just 1 updated shot each year
Approved for older adults and certain people 6 months and older
Cons
Doesn't guarantee that you won't get COVID (but helps prevent you from getting seriously sick)
Often causes temporary pain at the injection site, muscle pain, and tiredness
Pharmacist tips for Spikevax
A healthcare professional will give you Spikevax as an injection into your muscle. The vaccine is usually given at a pharmacy, a clinic, or sometimes a medical office.
Spikevax can cause mild side effects. This can include pain at the injection site, tiredness, muscle aches, and chills. They're normal signs that your immune system is working to build protection against COVID. These side effects should go away in a few days.
To help relieve arm pain and soreness, hold a cool, wet washcloth over the area where you got your Spikevax shot. Moving your arm around can also help with soreness.
Remember to get some rest and take it easy if you have a fever after you get Spikevax. Drink plenty of fluids to stay hydrated.
It's not recommended to take over-the-counter medications before your Spikevax shot to try to prevent side effects. This includes ibuprofen (Advil), acetaminophen (Tylenol), and antihistamines like diphenhydramine (Benadryl). We don't know how taking these medications beforehand might affect how well the vaccine works.
After your Spikevax shot, ask a healthcare professional what medications you can take to help with side effects if needed.
Get medical help if any side effects get worse after 24 hours of getting the Spikevax shot. Also reach out to a healthcare professional if side effects don't seem to go away after a few days.
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Frequently asked questions about Spikevax
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What are the risks and warnings for Spikevax?
Spikevax can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Heart inflammation (swelling)
Risk factors: Males between 12 and 24 years old
Although very rare, Spikevax has been linked to a higher risk of heart inflammation. This includes myocarditis (swelling of the heart muscle) and pericarditis (swelling of the tissue around the heart).
From reported data, this risk has been higher in males between 12 and 24 years old. Symptoms have typically shown up in the first week after vaccination. Most people recover within a few days after they get medical help and supportive care.
Call a healthcare professional right away if you have possible signs of heart inflammation after your Spikevax shot. Look out for chest pain, shortness of breath, or a racing heart.
Possible fainting after vaccination
Some people have fainted shortly after getting vaccines that are injected into the muscle. Tell the healthcare professional if you've ever fainted after a vaccination. They can keep a close eye on you for about 15 minutes after you get Spikevax to make sure everything is okay. To prevent getting hurt from fainting, it's best to sit down to get your shot and while the care team is watching you.
Lowered response to Spikevax in people with a weakened immune system
Risk factors: Medical conditions that weaken the immune system | Taking medications that lower the activity of the immune system
Spikevax might not work as well for people with a weakened immune system. This means they could still get very sick from COVID-19, even after getting the vaccine.
Before getting vaccinated, tell your care team about your health problems and any medications you take. Some conditions, like human immunodeficiency virus (HIV) and cancer, can weaken the immune system. And some medications, like high-dose steroids and transplant medications, can also make your immune system weaker.
If you have a weak immune system, keep taking steps to protect yourself from COVID. Talk to a healthcare professional about more ways to prevent getting sick.
Spikevax dosage forms
Typical dosing for Spikevax
Spikevax is injected into the muscle by a healthcare professional.
People ages 12 years and older: The typical dose is 1 injection (0.5 mL) into the muscle for the year. If you've already gotten a COVID vaccine in the past, wait at least 2 months before getting another dose.
Children ages 2 through 11 years: The typical dose is 1 injection (0.25 mL) into the muscle for the year. If your child has already gotten a COVID vaccine in the past, wait at least 2 months before getting another dose.
Children ages 6 months through 23 months
Never been vaccinated with any COVID vaccine before: The typical dose is 1 injection (0.25 mL) of Spikevax into the muscle. This is followed by a second dose of Spikevax a month later.
Have received 1 COVID vaccine before: The typical dose is 1 injection (0.25 mL) into the muscle for the year. It should be given a month after the last Spikevax dose they got.
Have received 2 or more COVID vaccines before: The typical dose is 1 injection (0.25 mL) into the muscle for the year. It should be given at least 2 months after the last Spikevax dose they got.
How much does Spikevax cost?
Spikevax contraindications
Previous severe allergic reaction to Spikevax
What are alternatives to Spikevax?
Prevention of COVID-19 infection in people 65 years of age and older
Prevention of COVID-19 infection in people between 6 months and 64 years old with at least one condition that puts them at high risk of serious problems from illness
Prevention of COVID-19 infection in people aged 12 years and older
Prevention of COVID-19 infection in people 65 years of age and older
Prevention of COVID-19 infection in people ages 5 to 64 years old with at least one condition that puts them at high risk of serious problems from illness
What is the latest news about Spikevax?
Spikevax images
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References
Best studies we foundAmerican Lung Association. (2025). Preventing COVID-19.
Berg, S. (2023). What doctors wish patients knew now about COVID-19 risk and age. American Medical Association.
Centers for Disease Control and Prevention. (2025). People with certain medical conditions and COVID-19 risk factors.
Chalkias, S., et al. (2025). Efficacy, immunogenicity, and safety of a next-generation mRNA-1283 COVID-19 vaccine compared with the mRNA-1273 vaccine (NextCOVE): Results from a phase 3, randomised, observer-blind, active-controlled trial. The Lancet Infectious Diseases.
Immunize.org. (2023). Fainting related to vaccination: What you need to know.
MedlinePlus. (2024). Myocarditis.
MedlinePlus. (2024). Pericarditis.
National Human Genome Research Institute. (2025). Antibody.
National Human Genome Research Institute. (2021). Understanding COVID-19 mRNA vaccines.
U.S. Food and Drug Administration. (2025). Spikevax.
U.S. Food and Drug Administration. (2025). Spikevax (COVID-19 Vaccine, mRNA) injectable suspension, for intramuscular use [package insert].
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