Dr. Roach: Fourth dose of COVID vaccine recommendations

Keith Roach
To Your Health

Dear Dr. Roach: My wife and I are both in our late 60s. She has gotten three doses of the Pfizer vaccine, and I have gotten three doses of the Moderna, only because that was what was available when we got our first dose. Because of our age, we are considering getting a second booster dose. I know the recommendation is that either vaccine would be fine, but we’ve heard that since the two vaccines attack the virus differently, it might be a good idea to switch vaccines, so I would get the Pfizer and she would get the Moderna. What are your thoughts?

— T.A.

Dr. Keith Roach

Dear T.A.: It is indeed true that the Moderna and Pfizer vaccines, although very similar, do have different effects on the immune system. So there are some experts who recommend switching vaccines, just as you’ve suggested. Both vaccines are excellent at preventing severe disease and at raising antibodies, but the types of antibodies are a little different, and the effects on T-cells, the other main arm of the immune system, are also different. Most of the studies showing benefit have used boosters of the same type as the original series, so that’s also a perfectly good option. I took my fourth dose using the mRNA vaccine booster that was different from the last three I had gotten.

Initial studies looking at booster shots that have been optimized for the omicron variant have not shown better outcomes than the original vaccine, so I would not wait for a new formulation. Those who are in the group recommended for a fourth dose by the Food and Drug Administration (all adults who received the Johnson & Johnson vaccine, and anyone over 50 or with moderate to severe immunocompromise who had their third dose four or more months ago) should consider getting their vaccine now. I recommend those at highest risk, such as older adults (over 75, or in a nursing home), those with diabetes or those with immune deficiency such as organ transplant, get a vaccine now.

People who had a recent (within one year) confirmed COVID infection AND three doses of vaccine have a high level of protection and probably do not need a fourth dose.

Dear Dr. Roach: If one takes blood pressure medication (losartan) in the evening, is it OK to eat grapefruit in the morning? Are there other foods that can interfere with blood pressure medications? Does the time of day make a difference?

— D.L.

Dear D.L.: Grapefruit juice can interfere with metabolism of some drugs, making some more toxic and others less effective. There are only a few drugs where this effect is large, such as some HIV medicines. Losartan and grapefruit juice have minimal interaction.

Sometimes, separating the drug and grapefruit juice is enough to eliminate the interaction, but in other cases, grapefruit juice should be enjoyed only sparingly or not at all. Your pharmacist is the expert in this.

The major food concern with losartan is high potassium foods. A few people, such as those with kidney disease, may need to limit potassium intake while on losartan or similar medicines. Your doctor is the expert in this.

Readers may email questions to ToYourGoodHealth@med.cornell.edu.