More than 34 million Americans have received Covid vaccines, but the much-touted system the government developed to monitor dangerous reactions has been unable to analyze safety data for weeks or months, according to numerous federal health agencies.

Currently, federal regulators anticipate a patchwork of existing programs that they acknowledge to be inadequate due to small sample sizes, lack of critical data, or other issues.

Clinical studies have shown that both US-approved vaccines – Pfizer-BioNTech and Moderna – offer high levels of protection against the coronavirus and are safe. But even the best studies have limited ability to identify rare side effects that occur only in certain populations or occur beyond three months.

In interviews, FDA officials confirmed that a promised surveillance system officially known as the Biologics Evaluation Safety Initiative, but commonly known as BEST, is still under development. They expect to start analyzing vaccination safety data soon, but probably not for a month or two.

The government currently relies mainly on a 30-year-old monitoring system that relies on patient and healthcare provider self-reporting known as VAERS (Vaccine Adverse Event Reporting System), as well as a smartphone app that vaccinated people can download and use it to report problems.

Few serious problems have been reported through these channels to date and no deaths have been clearly linked to the vaccines. There have been some severe allergic reactions but these are treatable and considered rare. To date, the rate at which the potentially fatal reaction known as anaphylaxis has occurred – 4.7 cases per million doses for the Pfizer BioNTech vaccine and 2.5 cases per million for Moderna – is consistent with the rate of other widely used vaccines.

Bruising and bleeding caused by decreased platelet counts have also been reported, although this could be accidental. A total of 9,000 adverse events were reported, of which 979 were classified as serious and the remainder classified as non-serious according to the latest available CDC report.

In interviews, public health experts, including current and former FDA and CDC officials, said funding shortages, turf wars and bureaucratic hurdles have slowed BEST’s progress.

But BEST will also suffer from a data problem that hinders existing systems. Because the vaccines are free, there is a lack of health insurance claims showing who received which vaccine and when – information that is vital to tracking vaccine safety.


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