This week, European Union countries including France, Germany, and Italy announced it would stop using AstraZeneca’s COVID-19 vaccine. That’s due to reports of blood clots in some recipients. But the drug maker, the World Health Organization, and the European Medicines Agency say there’s no evidence of a link between the forming of blood clots and the vaccine.
The stoppage has perplexed members of the medical community, including Dr. Edward Jones-Lopez, an assistant professor of medicine at the Keck School of Medicine at USC. He’s also an investigator of the AstraZeneca vaccine trial in the U.S.
He says the evidence supporting the decision is weak — only about 30 patients in all of the EU developed blood clots. “That is a relatively small number when compared to the expected number, particularly when you think of the populations that are getting this vaccine. [They] are typically older individuals with a slew of other comorbidities and also an increased risk of clots,” Jones-Lopez says.
He adds that so far, all vaccines have proven to be safe, with less than 1% of side effects now being considered as dangerous. That’s because each vaccine has gone through “exhaustive” protocols, including animal models and multi-phased human trials.
Jones-Lopez says many vaccines are also in the middle of a two-year follow-up, which are designed to detect rare side effects.
“Right now, the safety signals are somewhat incomplete in terms of length of follow-up. But there is absolutely nothing to be of concern. On the contrary, the efficacy data that is accompanying those safety data is so good that there's very clear indication from a medical standpoint, from a public health standpoint, to vaccinate as many people as possible.”
The efficacy of vaccines against coronavirus variations
According to Jones-Lopez, many of the vaccines were developed early in the pandemic, which might explain a lower efficacy against new COVID-19 variants.
“There's now some even immunological, blood-based data — that is not quite the same as efficacy data, but it's informative — that suggests that even these very efficacious vaccines … may be a little less efficacious against these variants.”
He points to two strategies to combat variants: accelerating the rate of vaccinations and developing new vaccine versions to specifically target already-identified variants.