Although the FDA has authorized the use of the Pfizer and Moderna "Omicron-specific" vaccines (which include components targeting both the Omicron and the original, Wuhan strain of the virus), there are no human clinical data available to support the vaccines' efficacy or safety, Dr. Anthony Fauci has stated.
According to Dr. Fauci, there "wasn't enough time" to conduct normal clinical trials, as Omicron is still spreading and taking lives.
Human data are available for the BA.1 subvariant of SARS-CoV-2. However, for the now-predominant BA.4 and BA.5 variants, only animal data from a small number of mice (eight) are available, and all the mice in the trial, both in the trial and in the control cohort, contracted COVID-19 during the study.
However, the mice were said to have had an "increased response" to the Omicron variants tested.
The new bivalent vaccines, like the original vaccines did at first, only have an emergency use authorization, which is given by the FDA in cases where there is an absence of any other effective treatment for a dangerous disease.
“I’m uncomfortable that we would move forward—that we would give millions or tens of millions of doses to people—based on mouse data," said Dr. Paul Offit, a member of the FDA's vaccine advisory committee, in comments published by the Wall Street Journal.