In the last few weeks, the FDA has started to limit COVID vaccine approvals, limiting their use in healthy people under 65 years of age, and HHS Secretary Robert F. Kennedy Jr. appeared to unilaterally take down CDC guidance that recommended their use in pregnant women and healthy children.

The rewriting of government recommendations will make the effort to get vaccine doses into arms exponentially more difficult, experts say.

Health Secretary Robert F. Kennedy Jr.'s intervention in COVID-19 vaccine recommendations without input from a key U.S. CDC advisory panel has sown confusion among physicians and insurers over who should get the shots and whether they will be covered,