The sisters received their first shots this past February at the University of Massachusetts Medical School in Worcester. During their appointments, which lasted about three hours, doctors asked the girls about their medical histories and explained the purpose of the trial.
Researchers also told them that not all trial participants would get the actual vaccine. Some would be given a placebo, an injection of a substance that contains no medication at all. Placebos are often used in clinical trials to help researchers compare groups of participants and determine whether vaccines are effective.
The girls got their second shots about four weeks later. After each injection, they had to use an app to answer questions about how they were feeling every day for a week.
Both of the sisters’ arms were sore, and Esme developed a rash around the injection site. But neither experienced some of the other short-term side effects of the vaccine that have been common in adults, such as chills or muscle aches, which may signal that the body is building protection against the virus. Researchers will continue to monitor all study participants, including Esme and Zoe, for more than a year.
For now, the girls don’t know whether they got the vaccine or a placebo, but they’re optimistic they got the real thing. “Then I’d be one of the first kids to get it,” says Esme.