COVID vaccine: What shot should I give and what shot should you get?

COVID vaccine: What shot should I give and what shot should you get?
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My patients all want "the shot." I have received dozens of calls and emails and texts every day, asking for a dose of COVID-19 vaccine. One of the main reasons I can’t say "yes" to their requests is that I, and other primary care doctors generally, aren’t the ones administering it. 

We don’t have the deep freezers needed for the Pfizer shot. Many of us don’t have the extra staff and logistics useful for the Moderna shot. Large vaccination centers, stadiums, clinics and a growing number of pharmacies are where people are going for their COVID-19 vaccines, which now number close to 2.5 million shots administered across the country each day.

But Johnson & Johnson’s Janssen vaccine that was just approved by the Food and Drug Administration (FDA) with an emergency use authorization (EUA) may change the playing field. Keep in mind that close to half of the vaccines in the U.S. are usually given out by primary care providers. Many of those doctors are adept at overcoming vaccine hesitancy by talking to our patients on a one-on-one basis. In an interview with me about vaccine hesitancy in the Black community, former U.S. Surgeon General Jerome AdamsJerome AdamsFormer surgeon general: 'Unconscionable' for states to ban mask mandates Former Trump surgeon general says politicians are 'taking tools' away from public health offices Pence urges young conservatives to get COVID-19 vaccine MORE emphasized the need for repetition and to explain our reasoning about why the vaccine is so important. “If you want people to care about what you say, they have to know you care about them,” he said.


The Johnson & Johnson vaccine uses a viral vector (adenovirus) that has been deactivated but carries a genetic payload into our bodies, signaling our cells to make the virus’s spike protein and provoke an immune response.

It is a relatively new technology, but unlike the MRNA vaccines, I can store it in my refrigerator for three months before use and then leave it out for hours in between patients. One shot of this vaccine has been studied and found to be close to 70 percent effective at decreasing the spread of COVID-19, more than 85 percent effective at preventing severe SARS-CoV-2 and 100 percent effective at preventing COVID-19-related hospitalizations and death. FDA data also shows that it decreases spread of the virus, which will help greatly in the fight for herd immunity.

But perhaps the most useful fact about the newly approved vaccine is that it has been studied in clinical trials for one shot and the immune protection has been found to be enduring. This is in contrast to the Messenger RNA vaccines (Pfizer/BioNTech and Moderna), which have only been studied for two shots. Scientists suspect that the immune protection lasts after one shot, but they haven’t proven it. Studies have also shown a big rise in neutralizing antibodies several days after receiving the second shot. This is particularly important when it comes to trying to safeguard the community against emerging partly resistant variants.

I would therefore try to give both shots of the MRNA vaccines, except when a patient who had COVID-19 is vaccinated. In this case, a study from the United Kingdom published in Lancet showed that antibodies and T cells rose as rapidly after one shot as they did after two shots in a patient without COVID-19. For a patient who had COVID-19, the Pfizer or Moderna or Johnson & Johnson vaccines can serve as a booster and one shot appears to be sufficient.

When it comes to the Johnson & Johnson vaccine, there may also be a role for a second shot given as a booster, perhaps retooled to cover emerging variants (including the one that emerged in South Africa), but the trials of the usefulness of the second shot are currently ongoing.


I will still tend to recommend the MRNA vaccines for my elderly patients because the Johnson & Johson shot wasn’t as effective for this group, especially if they had underlying medical conditions like diabetes or high blood pressure. Close to 50 percent of those over the age of 65 (the group with 80 percent of the deaths and a large majority of severe SARS-CoV-2) have already received at least one vaccine dose, which is a major reason that COVID-19 hospitalizations have dropped below 50,000 for the first time since November.  

The road out of this pandemic includes a stop at a vaccination site.

My office and other doctors’ offices across the country are ready and willing to augment our medical arsenal with the just-approved Janssen adenovirus vaccine. If I had this vaccine on hand, not only could I discuss the great safety and effectiveness of it compared with the dangers of the virus itself, but I could seal the deal by asking you to roll up your sleeve.

Marc Siegel, M.D., is a professor of medicine and medical director of “Doctor Radio” at NYU Langone Health. He is a Fox News medical correspondent and author of the new book, “COVID: the Politics of Fear and the Power of Science."