There are currently four licensed COVID-19 vaccines in the United States, and the number of shots you need depends on your age, health status, and how many doses you’ve already received. The system has shifted significantly since the early pandemic days of a two-dose primary series plus boosters. COVID-19 vaccination now follows a seasonal model, similar to the flu shot.
The Four Available Vaccines
The FDA has licensed four COVID-19 vaccines for use in the U.S. Two are mRNA vaccines: Comirnaty (Pfizer-BioNTech) and Spikevax (Moderna). A third mRNA vaccine called MNexspike is also licensed. The fourth, Nuvaxovid (Novavax), uses a different technology called a protein subunit, which delivers a lab-made version of the virus’s spike protein along with an ingredient that strengthens the immune response.
All four target recent strains of the virus. Each season, the formulas are updated to match whichever variants are circulating, just as flu vaccines are reformulated each year.
How Many Doses You Need Now
If you’ve never received any COVID-19 vaccine, you’ll typically need an initial multi-dose series before getting a seasonal dose. The exact number of shots in that starter series depends on your age and which vaccine brand you receive.
If you’ve been vaccinated before, the current recommendation is simpler: one updated seasonal dose. For the 2025-2026 season, the CDC recommends a single updated vaccine for people ages 6 months and older. This replaces the earlier system of primary series plus first booster, second booster, and bivalent booster that many people remember from 2021 through 2023.
The recommendation now uses what the CDC calls “individual-based decision-making,” meaning you and your doctor weigh the benefits based on your personal risk. The agency emphasizes that the benefit is strongest for people at higher risk of severe illness, including adults 65 and older and those with chronic health conditions. For healthy adults under 65, the decision is more personal.
Doses for Immunocompromised People
People who are moderately or severely immunocompromised follow a different schedule. If you’ve never been vaccinated, you start with the same initial multi-dose series, but after completing it and receiving an updated seasonal dose, you may be eligible for additional doses. These extra shots can be given at least two months after your last updated dose, based on a conversation with your healthcare provider.
This flexibility exists because immunocompromised individuals often don’t mount as strong an immune response from a single dose, so more frequent vaccination can help maintain protection.
How the Schedule Changed Over Time
The original COVID-19 vaccines, authorized in late 2020, required a two-dose primary series spaced a few weeks apart. Over the following years, additional booster doses were added as immunity waned and new variants emerged. At various points, some people were eligible for a third, fourth, or even fifth shot depending on their age and health status.
In 2023, the system shifted to a single annual updated dose, mirroring the approach used for influenza. The 2024-2025 vaccines from Pfizer-BioNTech, Moderna, and Novavax were the first full season under this model, targeting strains circulating at the time. The 2025-2026 vaccines continue this approach, with all three manufacturers offering updated formulations.
Young Children and Infants
Children as young as 6 months are eligible for COVID-19 vaccination. The number of doses a young child needs depends on their vaccination history and age. Children who have never been vaccinated require a multi-dose starter series before receiving the current seasonal vaccine, while those who have been previously vaccinated typically need just one updated dose. Your child’s pediatrician can determine the right number based on their specific situation.
Common Side Effects
Side effects from all four vaccines are generally mild and short-lived. The most common is soreness at the injection site. Fatigue, headache, muscle pain, joint pain, chills, and fever are also frequently reported with both the mRNA and protein subunit vaccines. Moderna’s vaccine may also cause nausea or vomiting in some people. In infants and toddlers, the most common reactions are irritability, decreased appetite, and sleepiness.
A rare but closely monitored side effect of the mRNA vaccines is myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the heart’s outer lining). Most patients who develop either condition after vaccination respond well to medication and rest and recover quickly.