What We Know About Covid Vaccines and Delta

Fully vaccinated people aren’t likely to get super sick from delta, but they can probably get mildly sick and pass it on to others

Photo: Ivan Diaz/Unsplash

The past two weeks have felt confusing, frustrating, and sudden for many people. As Covid-19 infection rates declined more and more throughout the summer, things started to feel a bit more normal-ish for many people.

Some felt like the pandemic was finally ending despite public health experts warning that it wasn’t and that another wave would arrive by fall. And then — BAM! — seemingly out of nowhere, the delta variant hit hard and fast. It’s now responsible for 83% of all infections in the U.S.

Now, just as families and schools are preparing for the upcoming school year, people are scrambling for answers, starting with the biggest one: How effective are Covid-19 vaccines against the delta variant? People who have been vaccinated and had begun feeling comfortable going maskless to stores, restaurants, and other places are now less certain about how protected they are. So let’s review the data we have so far.

Key takeaways

• The mRNA vaccines (Pfizer and Moderna) are extremely effective at preventing severe disease and hospitalization from the delta variant.
• The mRNA vaccines are less effective at preventing infection than disease, but the numbers vary on how much.
• The Johnson & Johnson vaccine is much less effective against infection with delta, but it protects well against severe disease.
• The rate of breakthrough infections in vaccinated people will be higher with delta than with past variants.
• We don’t yet have good data on the risk of vaccinated people transmitting delta to others, but most likely, vaccinated people can develop infections and pass the virus to others, vaccinated or not. In other words, if you’re fully vaccinated, assume it’s possible for you to get delta and give it to others.
• Immunity from natural infection (before delta) seems to protect almost but not quite as well against severe disease as the vaccines, but it probably doesn’t protect well against infection or transmission. In…