A recently released paper by the National Institutes of Health on boosters—which has yet to be peer reviewed—showed that recipients of the Moderna booster shot had the highest antibody levels out of all the vaccines. Although the dose given in the study was higher than the CDC’s recommended half-dose, the results indicate that Moderna’s booster has a significant effect in offering greater protection against COVID-19.

Here’s what you need to know about who’s authorized to receive a Moderna booster. 

If you got the Moderna vaccine

If you originally had the Moderna COVID-19 vaccine, the CDC recommends a half-dose booster for people over 65 or younger people who are at high risk of contracting COVID-19, who had their second dose more than six months ago. High risk is defined as having an underlying medical condition that can make you more susceptible to the disease, like diabetes or cancer, or working in a hospital, school, or grocery store. 

If you got the Pfizer or Johnson & Johnson vaccine

The FDA and CDC also approved mixing and matching of COVID-19 vaccines, meaning that even if you didn’t initially receive the Moderna shot, you’re still eligible for the half-dose booster (or a booster of either the Pfizer or Johnson & Johnson vaccine instead). If you’re a Pfizer recipient, you’re eligible for a booster if you had your second dose more than six months ago and are over 65 or at high risk of contracting COVID-19 because of medical conditions or your job.

The CDC is recommending that all recipients of the Johnson & Johnson COVID-19 vaccine receive a booster after two months of being vaccinated. You can receive either a half-dose of Moderna or a full dose of the Pfizer or Johnson & Johnson vaccine.

Where can I get a Moderna booster shot?

A spokesperson for the National Association of Chain Drug Stores said pharmacies were “closely coordinating” with the CDC to prepare Moderna and Johnson & Johnson boosters. Walgreens said it had already started administering the shots in its U.S. stores.