Question: Are there significant differences in type and severity of side-effects from the various currently available vaccines worldwide?  Some of my family members in Europe are hesitant to get vaccinated with Astra-Zeneca because of things they’ve “heard,” and seem to favor the other vaccines, while I don’t think waiting until the other vaccines are available is a good idea. Any reputable resources of comparisons that I might be able to point them to?

Answer: Available evidence indicates that there are no significant differences in the type and severity of side-effects from the Pfizer, Moderna, Johnson & Johnson, and AstraZeneca vaccines.  All four vaccines are safe and effective at preventing severe disease (100% efficacy in clinical trials at preventing hospitalization and death).  Public health experts recommend that individuals take whatever vaccine offered.  As Dr. Fauci recently stated, “…people should take the [vaccine] that’s most available to them… If you go to a place and you have J&J and that’s the one that’s available now, I would take it. I personally would do the same thing. I think people need to get vaccinated as quickly and as expeditiously as possible.”     

When it comes to comparing the three vaccines currently available through FDA authorization in the US– Pfizer, Moderna, and Johnson & Johnson– helpful comparison tables abound.  One note of caution– comparing efficacy rates between vaccines is a bit like comparing apples to oranges; because the vaccines were tested at different times and in different places, you can’t make direct efficacy comparisons.  That said, I think this chart (Figure 1) from the Delaware Department of Health is especially easy to read, though it doesn’t include the side effects piece.  Meanwhile, the Association of State and Territorial Health Officials (ASTHO) maintains an updated comparison chart with more detail for the three authorized vaccines.  And Business Insider offers a helpful interactive visualization of all four vaccines (Figure 2).  If you’re looking for more detailed information, these FDA Fact Sheets for Pfizer, Moderna, and Johnson & Johnson are all useful and relatively easy to read (as FDA documents go). 

Finally, I know some people have been concerned about severe allergic reactions, which remain rare and treatable (see Q&A for 3/12). And I know that the latest AstraZeneca scare is also put people on edge.  There is, however, no proven causal link between the vaccine and the rare occurrence of blood clots (25 cases out of 20 million vaccinated), and just last week, the European Medicines Agency stated, “COVID-19 Vaccine AstraZeneca is not associated with an increased overall risk of blood clotting disorders.”  We’re still waiting on AstraZeneca’s US clinical trial data to be made publicly available.  Apparently the company made yet another misstep yesterday by releasing outdated information about its efficacy findings.  The company has made several missteps over the last several months (detailed in this STATNews report) that make it harder to win people’s trust.  Hopefully the detailed findings soon to be released from AstraZeneca’s US-based clinical trial will further put people’s concerns to rest.

Figure 1. Comparing Vaccines (from Delaware Department of Health)

Figure 2. Comparing Vaccine Side Effects (from Business Insider)