COVID-19 vaccines: Study finds J&J recipients better off with Moderna, Pfizer booster

According to a study by the National Institutes of Health on whether or not it is safe to "mix and match" COVID-19 vaccines found that people who received the single-dose Johnson & Johnson shot are better off getting a booster from Pfizer or Moderna. 

The study, which has yet to be peer reviewed, was released Wednesday and found that people who initially got the J&J vaccine displayed better protection when they got Moderna or Pfizer’s mRNA vaccine as opposed to another dose of the J&J vaccine, identified by its scientific name Ad26.COV.S.

"Persons who received an mRNA-based booster vaccination had a four-fold increase in their neutralization response more frequently than those who were boosted with Ad26.COV.S," study authors wrote.

The study consisted of 450 adults who received one of the three available vaccines in the United States. Researchers looked for any benefits or drawbacks when participants used different vaccines for boosters and found that regardless of which was used as a booster dose, antibody levels which protect the body from the virus increased, though Moderna and Pfizer provided greater protection. 

No serious side effects were found when mixing vaccines, but two participants vomited while two others who received a J&J booster experienced fatigue or insomnia. 

Researchers said that based on their data, if mixing vaccines is met with federal approval, people would get an immune response by taking a booster regardless of the maker of their initial shot. 

"These data suggest that if a vaccine is approved or authorized as a booster, an immune response will be generated regardless of the primary Covid-19 vaccination regimen," researchers wrote in the study. 

"Heterologous prime boost strategies may offer immunological advantages to optimize the breadth and longevity of protection achieved with currently available vaccines," heterologous meaning "having a different relation," according to Oxford dictionary. 

What is the difference between the 3 vaccines?

The vaccines developed by Moderna and Pfizer-BioNTech operate through a newer delivery system called mRNA, or messenger RNA, technology. 

Johnson & Johnson’s vaccine involves a more traditional modified adenovirus vector vaccine with a durable protein exterior encasing the DNA, lending itself to a longer shelf-life.

To create the vaccine, the Johnson & Johnson team took a harmless adenovirus – the viral vector – and replaced a small piece of its genetic instructions with coronavirus genes for the SARS-CoV-2 spike protein.

After the modified adenovirus is injected into someone’s arm, it enters the person’s cells. The cells then read the genetic instructions needed to make the spike protein and the vaccinated cells make and present the spike protein on their own surface. The person’s immune system then notices these foreign proteins and makes antibodies against them that will protect the person if they are ever exposed to SARS-CoV-2 in the future.

The adenovirus vector vaccine is safe because the adenovirus can’t replicate in human cells or cause disease, and the SARS-CoV-2 spike protein can’t cause COVID–19 without the rest of the coronavirus.

On the other hand, messenger RNA vaccines use genetic instructions from the coronavirus to tell a person’s cells to make the spike protein, but these don’t use another virus as a vector. There are many practical differences, too.

The Johnson & Johnson vaccine can also be stored at much warmer temperatures than the mRNA vaccines. The mRNA vaccines must be shipped and stored at below–freezing or subzero temperatures and require a complicated cold chain to safely distribute them. The Johnson & Johnson vaccine can be stored for at least three months in a regular refrigerator, making it much easier to use and distribute.

The Associated Press contributed to this story.