White people and women are consistently overrepresented in U.S. vaccine trials while some racial and ethnic minorities and men are underrepresented, according to a new study of more than 200 trials. 

Conducting vaccine trials on groups of subjects who are representative of the general population is crucial, the researchers wrote in a paper published in JAMA Network Open on Friday, because medicines may affect different groups of people in varying ways. 

Excluding minority groups from trials may also discourage trust in vaccinations, according to the researchers. 

“We’re making an assumption that these treatments are appropriate for certain groups when they may not be,” said first-author Laura Flores, a joint M.D. and Ph.D. student at the University of Nebraska Medical Center. “I really think we can do better.” 

Flores and her co-authors examined 230 U.S.-based vaccine trials with more than 200,000 participants conducted between 2011 and 2020. They found that 77.9% of adult participants in the trials who reported ethnicity were white, despite white people making up just 74.1% of the population in 2011 and 76.3% in 2018. By contrast, 10.6% of participants were Black, even though Black people constituted 12.6% of the U.S. population in 2011 and 13.9% in 2018. 

The disparity also extended to Hispanics, who counted for 16.7% of the U.S. population in 2011 and 18.5% in 2018 but made up just 11.6% of adult vaccine trial participants. And the gap was the widest for American Indian, Alaska Native and Pacific Islanders, who collectively made up 1% of the population in 2011 and 1.5% in 2018 but were just 0.6% of vaccine trial subjects. 

“Even small inequities are important inequalities, and we’re doing a genuine disservice to these populations by not reaching out,” said Flores. 

Interestingly, the race gap did not extend to Asians, who made up 5.7% of vaccine trial participants while constituting 4.8% of the American population in 2011 and 5.9% in 2018. 

The researchers also found that women made up 56% of adult vaccine study participants, even though they were just 51.5% of the U.S. adult population in 2011 and 50.8% in 2018. Flores said she was surprised women were overrepresented in her study because they have been underrepresented in certain other medical trials. She added that she was not sure what caused the disparity, but that women may have a greater overall interest in vaccine trials than men.

The study included trials that had been published by June 30 of last year, meaning COVID-19 vaccine tests were not included. Flores said, so far, though, coronavirus vaccine trials have been much more inclusive than those examined in her study. 

“The COVID trials have been surprisingly good about representation,” she said. “Moderna’s has been almost exactly reflective of the U.S. population” 

However, the distribution of vaccines within the U.S. has generally been skewed toward wealthier, whiter communities — though non-white Americans have died from the coronavirus at much higher rates. 

“The vaccination rates in white populations are significantly higher,” said Flores. “It’s eye-opening.” 

The researchers also highlighted what they consider to be an unacceptable lack of reporting around race and ethnicity in vaccine trials. 

Every trial they studied included the age and sex of participants, but just 58.3% reported race and 34.3% reported ethnicity. Ethnicity categorizes participants through cultural identities, such as Hispanic or Latino, while race includes physical classifications like white, Black and Asian.

While U.S. government agencies like the Food and Drug Administration recommend collecting such data, Flores believes they should consider making explicit rules. 

“If there are no teeth behind those guidelines, often they are forgotten,” she said. 

In vaccine trials, researchers record skin redness around the injection site to the millimeter, Flores said — so noting a participant’s skin color should not be very difficult. 

“Collecting race and ethnicity data should not be an undue burden,” she said. 

Flores said she saw parallels between her study and a recent article about a study that shows white police officers in Chicago are more likely to use force and make arrests. While the research areas are quite different, Flores said authors of both studies are asking institutions to collect and distribute better data. 

“These researchers are asking for transparency and better reporting,” she said. “We’re doing that, too.” 

The study, titled “Assessment of the Inclusion of Racial/Ethnic Minority, Female, and Older Individuals in Vaccine Clinical Trials,” was published in JAMA Network Open on Feb. 19. The co-authors are Laura Flores of the University of Nebraska Medical Center; Walter Frontera of the University of Puerto Rico School of Medicine; Michele Andrasik, Elizabeth Krantz and Steven Pergam of the Fred Hutchinson Cancer Research Center; Carlos del Rio of Emory University, Antonio Mondríguez-González of the Universidad Central del Caribe; Stephanie Price of Helen Keller International and Julie Silver of Harvard Medical School.