Dr. Mark E. Horowitz getting his Moderna. His expert opinion: “The best vaccine is the one you can get soonest.”

By S. Mitra Kalita

Editor’s Note: We texted with Dr. Horowitz this morning (April 13) in light of a report that the J&J vaccine was being paused after six women developed blood clots after receiving it; one died. His suggestion was to similarly pause booking people for it until we know more. 


Our Epicenter volunteers keep hearing from people requesting a specific vaccine. This is often not per doctors’ instructions but because of something they heard from a friend or on the news. We asked Dr. Mark E. Horowitz, a family doctor in downtown Manhattan and someone we trust, to respond to these concerns. Bottom line: “The best vaccine is the one you can get soonest.”

Epicenter: Dr. Horowitz, we keep hearing from people who have a preference for a particular vaccine. Can you tell us if some vaccines are better for certain groups over others? 

Dr. Horowitz: The best vaccine is the one you can get soonest. All three currently available vaccines are highly effective and safe.

Most importantly, all three provide nearly 100% protection against severe disease and hospitalization. The small difference in efficacy between the Janssen (aka the Johnson & Johnson) vaccine and the Pfizer-Biontech and Moderna vaccines is not clinically significant, so people really don’t need to worry about it.

 Epicenter: What is the difference between the Moderna and Pfizer vaccines and how they work versus the J&J vaccine? Why do the former need two doses? 

Dr. Horowitz: The Pfizer and Moderna vaccines use the mRNA technology. They essentially trick the body into thinking the virus is present by using a laboratory-produced protein that looks like the spike protein of the coronavirus.  The Johnson & Johnson vaccine uses a viral vector. That is to say it uses a container made from a virus that does not infect humans (it infects chimpanzees) and places the coronavirus, in a non-infectious form, in that shell. All three vaccines stimulate the immune system to produce antibodies that attack the coronavirus if the vaccinated individual is exposed to it, neutralizing the virus.

 Epicenter: Should I be worried about the J&J vaccine? I read some concerning reports: one said a woman got Covid after getting a vaccine. Another said the plant made a bad batch. 

Dr. Horowitz: All of the vaccines take approximately two weeks to have their full effect.  So, it is conceivable that someone who is exposed to the virus around the time of the vaccine may still become infected. That’s why it is so important to continue to observe all the usual precautions (mask-wearing, social distancing and regular handwashing) even if you’re getting the vaccine.

 All of the doses of the Johnson & Johnson vaccine made at the factory in Baltimore that produced the defective doses have been destroyed. The company has taken over control of the factory and all subsequent batches are fine.



S. Mitra Kalita is a veteran journalist, media executive, prolific commentator and author of two books. In 2020 she launched Epicenter-NYC, a newsletter to help New Yorkers get through the pandemic. Mitra...

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