- AstraZeneca defended the safety of its coronavirus vaccine in an unusual statement Sunday after reports emerged of abnormal blood clots in some immunized patients in Norway and in Demark.
- Health authorities in Ireland, Norway, Austria, Italy and other countries have since slowed or temporarily suspended use of AstraZeneca's vaccine as a precautionary measure. But AstraZeneca responded by noting that 17 million people in the U.K. and Europe have been vaccinated and there is "no evidence of an increased risk" of pulmonary embolism, deep vein thrombosis or other bleeding events.
- The British drugmaker aims to reassure countries that its shot is safe, adding that the number of events seen in clinical testing and real-world use is lower than would be expected. Nonetheless, the situation is the latest controversy surrounding a shot that has already had numerous setbacks.
When a vaccine is moved from clinical tests to real-world use in millions of people, rare side effects can emerge that weren't observed within the confines of tightly controlled trials. So, too, can incidental illnesses that have nothing to do with the shot.
Discerning which cases are linked to vaccination can be difficult. But it is critically important work, as headlines highlighting apparent side effects can impact public perception of a vaccine's safety even if the events are later proven to be unrelated.
Following the authorization of vaccines from Pfizer and Moderna last year, reports of allergic reactions in a few vaccine recipients raised alarms and spurred regulators to place warnings on the labeling for each shot. More data now indicate allergic reactions are exceedingly rare, at a rate of about 5 or 2.5 events per million inoculations for Pfizer's and Moderna's vaccines, respectively. None have been fatal.
As of March 14, more than 107 million doses, mostly of the two companies' shots, have been administered in the U.S.
More recently, reports of bleeding under the skin in younger people receiving AstraZeneca's vaccine have emerged in Norway, with one case leading to death. The events spurred Norway and some other European countries to pause or slow their rollout of AstraZeneca's shot, though it is unclear whether the events were a result of vaccination or merely incidental. Europe's drug regulator is investigating the cases. A report should be issued this week and available to the public.
In the meantime, however, AstraZeneca faces a messaging problem. Confusing clinical results and limited trial data in the elderly have hampered its rollout in Europe, with some countries placing limitations on who should be vaccinated. That's appeared to have led to hesitancy in countries like Germany and France, reportedly resulting in thousands of doses going unused even though the shot is supported by the World Health Organization and authorized for use in more than 70 countries.
AstraZeneca is adamant that its vaccine isn't the cause of the observed blood clots. The company noted Sunday that there have been only 15 cases of deep vein thrombosis and 22 reports of pulmonary embolism across the more than 17 million people who have received its vaccine through March 8.
Those numbers are "much lower" than the hundreds of cases that would be expected in the general population and are "similar across other licensed COVID-19 vaccines." Instances in clinical testing were "small" and more common in the placebo group. There is no evidence of increased bleeding in the more than 60,000 enrolled volunteers, AstraZeneca said.
"The nature of the pandemic has led to increased attention in individual cases and we are going beyond the standard practices for safety monitoring of licensed medicines in reporting vaccine events, to ensure public safety," said AstraZeneca chief medical officer Ann Taylor, in the company's statement.
A real-world study in February showed the shot could significantly reduce hospitalizations and severe illness from COVID-19. Positive results and a clean safety profile in AstraZeneca's ongoing U.S. trial — its largest clinical test so far — could bolster support as well. Data are expected soon.
A recently published report indicated AstraZeneca expects to file for authorization in the U.S. either later this month or in early April if the study succeeds.