WASHINGTON — Officials at the Food and Drug Administration have blocked publication of several studies supporting the safety of widely used vaccines against COVID-19 and shingles in recent months, a spokesperson for the Department of Health and Human Services confirmed. The studies, which cost millions of dollars in public funds, were conducted by scientists at the agency, who worked with data firms to analyze millions of patient records. They found serious side effects to be very rare. In October, the scientists were directed to withdraw two COVID-19 vaccine studies that had been accepted for publication in medical journals. In February, top FDA officials did not sign off on submitting abstracts about studies of Shingrix, a shingles vaccine, to a major drug safety conference. The withdrawal of the studies is the latest step by the administration to try to limit access to vaccines.…