Mix and Match Vaccines

Angelina Huang ‘25

Despite the success of COVID-vaccine distributions, the controversial issue of vaccine boosters arises. While booster shots are imperative in making sure that antibodies can be strengthened and that levels of immunity are maintained, some are still skeptical of its effectiveness to combat the virus. 


Over the past year, many companies have created their own vaccine against the deadly virus. Among them, Pfizer and Moderna are two vaccine-makers that many people have heard of. Their vaccines use a new type of mRNA technology that contains genetic coding and operates by instructing cells to create a ‘spike protein’. This spike protein is also found in the virus itself, however, these mRNA vaccines are made to only attack the virus. 


On the other hand, Johnson & Johnson (J&J) went the traditional route, avoiding the mRNA approach. J&J vaccines do such by utilizing a disabled adenovirus that carries the genetic code for the SARS-2 spike protein. So far, research has shown that Pfizer and Moderna vaccines, of which required two doses, have a 95% efficacy rate, whereas the Johnson & Johnson vaccine, in one dose, only had an efficacy rate of 66%.  


As of October 2021, the F.D.A. has authorized a new strategy of vaccine distribution: the ‘mix and match’ method. This strategy recommends receiving two vaccines of different brands.


A recent NIH (National Institutes of Health) study of 450 people, called heterologous, tested those who had already had vaccines of Pfizer, Moderna, and Johnson & Johnson. After 4-6 months from their original vaccination process, they received additional doses of the three shots. 


Those who received a different booster from their original vaccine saw similar antibody increases to those who received the same, however there were a few differences. Given that the study was relatively small–with only 50 people on each of the 9 vaccine combinations, scientists do not have indefinite proof to conclude their research. 


When already given a J&J vaccine, a Moderna or Pfizer booster was shown to have had antibody levels 9.8 times greater than those with a J&J booster. Despite the lack of research, most scientists believe that the efficacy rate could be related to the difference in vaccine technology. However, those who already have had Pftzer or Moderna (mRNA technology) have less of a reason to use the Mix and Match approach. The studies show that there aren’t many differences in the antibody levels. 


Despite obvious results in increasing overall antibodies, the mRNA vaccines (Pfizer and Moderna) were found to have more spiked antibody levels compared to Johnson and Johnson’s.   The study concluded that Moderna vaccines slightly increased antibody levels than Pfizer’s but overall, had a similar effect and approach. 


Despite this, many are still dubious about the vaccine boosters, however, the risks are very small. Side effects of the booster include fever, headache, fatigue, and pain at the injection site, commonly lasting about 1-2 days. Moreover, people often put-off boosters as they believe that there is no additional benefit, but antibodies can actually decrease over time, increasing the public’s need for immunity boosters. 


Booster shots are currently available to people who are 65 years or older, or 18 years or older with underlying medical conditions, long-term settings, or high-risk working conditions. The CDC recommends that those who had gotten Pfizer or Moderna should receive a booster at least 6 months after original vaccination. Those who received Johnson & Johnson should subsequently get their booster at least 2 months after the first. 


[1] https://www.theatlantic.com/health/archive/2021/10/mix-match-booster-covid-vaccine/620395/

[2] https://www.nature.com/articles/d41586-021-02853-4


[4]https://www.cdc.gov/coronavirus/2019-ncov/vaccines/booster-shot.html?s_cid=11706:cdc%20 vivid%20booster%20 recommendations:sem.ga:p:RG:GM:gen:PTN:FY22