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.

Pfizer has also tested a BA.4- and BA.5-specific booster in mice, and they presented that data during an FDA committee meeting this week.

Relying on existing data will let the FDA and COVID-19 vaccine makers move more quickly to make booster shots available. But the virus is still spreading rapidly, and they may not be ready in time to stave off a BA.4 / 5 wave.

The FDA said it hopes to have new COVID-19 boosters available this fall. “This fall we have to go all out on our booster campaign,” said Peter Marks, head of the agency’s Center for Biologics Evaluation and Research.