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Your Good Health: Johnson & Johnson vaccine uses viral vector technology

Moderna, Pfizer shots use mRNA
Dr. Keith Roach

Dear Dr. Roach: Can you tell me why the Johnson & Johnson vaccinations only requires one shot to be considered fully vaccinated as opposed to the others that require two shots? I understand some vaccinations require a booster shot. But usually it’s months or a year or two before the second one is required, if I remember giving my kids their vaccinations and the scheduling requirements. And no, I’m not vaccinated yet. I have trouble with things that are being shoved down my throat, requiring me to sign off on my rights, as this obviously hasn’t been put through normal tests. I didn’t have to sign off on any vaccinations for all three of my children, so I’m not sure why they’re expecting me to sign off on these ones — other than the fact that they’ve been rushed and the manufacturing companies don’t want to be liable for the mistakes that they’ve possibly made.


Many vaccines require multiple doses. Maybe you’ve forgotten, but hepatitis B is three shots; DTaP is five shots; polio is four shots for the primary sequence. Our immune system is very good, but repeated exposure to a germ helps our immune system learn how to fight off invaders.

The Johnson & Johnson vaccine uses a viral vector technology, different from the Moderna or Pfizer vaccines, which use mRNA. All three of those vaccines are effective at preventing serious illness and death from COVID-19. Early data from the Johnson & Johnson vaccine showed very high effectiveness after one dose. However, data presented in October showed that giving a booster shot after the Johnson & Johnson vaccine dramatically improved the immune response. Giving a second dose of Johnson & Johnson increased the neutralizing antibody level in the blood more than fourfold. However, giving a booster dose of the Moderna vaccine to people who had a single dose of the Johnson & Johnson vaccine increased the neutralizing antibodies by 75-fold.

I do understand that nobody likes to be forced to get a medical procedure done, especially one, like COVID-19 vaccines, that has not been around a long time. There are some important reasons why you should still get it. The most important is that COVID-19 has killed over 5 million people worldwide as of this writing, including almost 750,000 in the U.S. and almost 30,000 in Canada. You really want protection from this deadly disease.

I’d also say that nobody is forcing you to get the vaccine (since you haven’t had it). However, businesses have the right to refuse you if you aren’t vaccinated, just like schools don’t allow children to enroll who don’t have their vaccines up to date. You certainly had to agree to your children getting vaccinated. You don’t give up your rights when being vaccinated. The National Vaccine Compensation Program and Countermeasures Injury Compensation Program provide benefits in the unlikely event of injuries caused by covered vaccines in the United States.

I’m also going to disagree that the processed has been rushed in such a way that mistakes are likely. It is true that the vaccines were approved faster than any other vaccine in history, but that corresponds to the normal testing being done more quickly than in previous vaccines. Truly enormous resources were put into the development and testing of these vaccines. More than 7 billion doses have now been given out, and the safety of the vaccine is very high. Serious side effects include allergic reactions, blood clotting problems and myocarditis (inflammation of heart muscle). The likelihood of a severe reaction is less than 1 in 10,000.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to

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