BOSTON (CBS) — Dr. Mallika Marshall is answering your coronavirus vaccine-related medical questions. If you have a question, email her or message her on Facebook or Twitter.

Brian writes, “I had the Moderna vaccine back in March. I then had a breakthrough of Covid in September. I was curious when and if I should get the booster?”

You probably got a nice boost in antibodies from having a natural breakthrough infection, but that immunity could wane over time as well. If you fit the criteria for a booster, you probably should get one at some point, probably within 90 days of having your infection, although there isn’t a lot of data to support what to do in your case. And there are a lot of people out there like you!

Diane writes, “My mom is 86. She received her flu vaccine yesterday, but her doctor is suggesting patients wait 2 weeks before getting a COVID booster. Should she wait or can I get her in for her booster?”

The CDC used to suggest you wait 2 weeks between vaccines but now the agency says you do not need to wait any time between getting a COVID-19 booster and other vaccines, including the flu vaccine.

Marianne says, “I read a news article about the Moderna booster and I’m wondering if a half dose is enough.”

The protection provided by the original two-dose Moderna vaccine regimen may be a little more durable than that provided by the Pfizer or J&J vaccines. There was even some discussion among health experts as to whether a booster would be needed at all after six months in people who had already received two Moderna doses, but it was decided some people would still benefit from a booster. So, I think it makes sense that the booster is offered at a lower dose, 50 mcg vs. 100 mcg, because a higher dose is probably not necessary and is likely to cause more side effects than a full dose.

Dr. Mallika Marshall