COVID-19 vaccine manufacturers won’t need to conduct new clinical trials as they develop booster shots targeting the most recent variants of the virus, a Food and Drug Administration official told Reuters.

The agency will use clinical trials of variant-specific boosters developed earlier in the pandemic, manufacturing data, and animal studies to evaluate the shots.

The omicron variant of the virus has developed into multiple lineages. Right now, the BA.4 and BA.5 variants are the most widespread in the United States. The FDA said Thursday that the next set of booster shots should be against those versions of the virus. But pharmaceutical companies have been testing shots targeting BA.1, an earlier omicron lineage. Early data from Moderna and Pfizer / BioNTech shows that those shots generate a strong immune response against the omicron virus — including the BA.4 and BA.5 lineages, although to a lesser extent than BA.1.