CAMBRIDGE (CBS) – Moderna said older patients are responding well to its coronavirus vaccine.

The Cambridge-based company announced Tuesday that half of the participants in its’ clinical trial are 71 or older.

The latest research, published in the New England Journal of Medicine, said the vaccine stimulated an immune response in many of them without serious side effects. The most common side effects of the vaccine are headaches, fatigue and chills lasting about a day.

As of last Friday, Moderna said 27,232 participants have enrolled in the third phase of its vaccine trial, which requires two doses. The company said 15,454 of them have received their second vaccination.