Martha writes:

Hi Dr. Griffin,

My parents are 85 and 92 years old, both are healthy and each received two Moderna vaccines, the 2nd of which was in April. They don’t have health issues that would compromise their immune system.

Given their ages, for their third shots, would you recommend they have the full dose Moderna or the half dose booster now?

Thank you,


Melanie writes:

Dear Dr Griffin,

It is rainy and 8C in Ottawa presently.

For those of us who received delayed dosing, is there any information on whether we are necessarily going to need a third shot? We are all being told that a third shot is inevitable, but most of that is based on short, roughly 3 week, protocols between doses one and two. I’m wondering if the signals are different for those who received delayed dosing. Who doesn’t want to avoid an extra shot in the arm, especially when those shots are so desperately needed elsewhere in the world!

Thank you kindly,


Hugh writes:

Dr. Griffin,

As a result of an auto accident I had my spleen removed when I was 36 years old. I am now a healthy 83 year old. To what extent am I immune compromised? And will I have a “normal” response to Sars-CoV-2 vaccine?


Laura writes:

Dear Dr. Griffin,

Thank you so much these weekly clinical updates. I’m just a lowly layperson but being able to hear thoughtful discussion of the latest Covid research has been immensely helpful to me. I feel that it gives me the ability to see through the media spin and see the nuance in the research rather than oversimplified talking points.

My question is about unvaccinated family members. My wife’s sister and brother-in-law would like to visit. They have been honest about the fact that they are not vaccinated nor do they plan on getting vaccinated. My wife and I are both fully vaccinated including our booster doses. We are very conflicted about how to address their desire to visit. Is having unvaccinated house guests in a fully vaccinated home a terrible idea? Other than all of us wearing N95 masks at all times and keeping the windows open and the ceiling fans on, are there any other ways to keep risk lowered? And last, are we overreacting to all of this simply because we have been so sensitive to every bit of Covid risk over the past year and a half?

Thank you for any advice you might have.

Best regards,


Mesilla Park, NM

Justin writes:

Our 5 yo daughter is quite small, on the low end of percentile for weight. 

Is there anything to be aware of with the vax that I assume is dosed for a higher percentile population?