Following an announcement by the Centers for Disease Control and Prevention (CDC) that individuals can mix and match booster shots, House Science, Space, and Technology Committee Ranking Member Frank Lucas joined Oversight and Investigations Subcommittee Ranking Member Jay Obernolte in a letter requesting clarification about the Administration’s decision-making process.  

“We are concerned that conflicting messages from federal health officials since the booster rollout was first announced are confusing the public and undermining confidence in the effectiveness of COVID-19 vaccines,” Obernolte and Lucas wrote. “We are also concerned that these conflicting messages will increase vaccine hesitancy and further fuel misinformation about the safety, effectiveness, and need for COVID-19 vaccines. Although evidence continues to show that COVID-19 vaccines are safe and effective at preventing illness and death from COVID-19, vaccine hesitancy remains a significant public health problem.”

Obernolte and Lucas detailed the disordered and conflicting messages about the booster shots beginning in August of 2021. On August 18, the Administration announced a plan to rollout boosters for the general population beginning on September 20. In the two months since, recommendations about the timing of booster shots, the populations that would benefit from booster shots, and the protocols for booster shots – culminating in a mix-and-match approach between booster types – have vacillated dramatically. During that time, many scientists expressed concerns about a lack of data and possible confusion created by unclear and conflicting recommendations.

“To increase vaccine uptake, it is critical that the Administration takes a deliberate, scientific approach to its vaccine recommendations, and communicates its decisions clearly and consistently to the public,” they wrote. “That has not been the case with the booster shots.” Obernolte and Lucas requested a briefing from FDA and CDC on the process surrounding booster recommendations, as well as the science, data, and other considerations that informed the Administration’s decisions.

Read the full letter here, and the timeline for the booster rollout below.


  • August 18, 2021: Department of Health and Human Services statement announcing a plan to begin offering booster shots of the Pfizer and Moderna vaccines for all Americans beginning the week of September 20. Boosters would be given starting eight months after an individual’s second vaccination dose.
  • August 18, 2021: Remarks by President Joe Biden reiterating this plan and timeline.
  • August 27, 2021: President Biden says the Administration is considering shortening the timeline to five months after an individual’s second dose.
  • August 27, 2021: White House Press Secretary walks back the President’s comments saying the timeline continues to be eight months after the second dose.
  • September 2, 2021: New York Times reports that the CDC and Food and Drug Administration (FDA) recommend that the Administration scale back the plan to offer boosters to the general population.
  • September 13, 2021: Now just a week before the announced general population rollout date of September 20, The Lancet medical journal publishes an opinion piece signed by two senior FDA officials stating that current evidence does not show a need for boosters for the general population.
  • September 17, 2021: The FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) recommends an emergency use authorization (EUA) for Pfizer boosters to recipients ages 65 and older and those at high risk of COVID-19 six months after their second dose, but rejects the application to recommend boosters for all adults.
  • September 22, 2021: FDA issues an EUA for Pfizer boosters to elderly and at-risk populations, at least six months after their second dose. FDA includes individuals 18 – 64 years of age with frequent institutional or occupational exposure to COVID. No mention is made of whether recipients of Moderna and Johnson and Johnson vaccines could be eligible for the Pfizer booster.
  • September 23, 2021: The CDC Advisory Committee on Immunization Practices (ACIP) recommends Pfizer boosters six months after primary vaccination to elderly and at-risk populations, but—contradicting the VRBPAC recommendation and FDA EUA—recommends against boosters for individuals with frequent institutional or occupational exposure to COVID.
  • September 24, 2021: CDC Director Rochelle Walensky overrules the ACIP’s decision not to recommend boosters for individuals in high risk occupational and institutional settings, to align with the FDA EUA and expand eligibility of the Pfizer booster to more populations. 
  • October 13, 2021: FDA publishes an analysis of Johnson & Johnson’s application for a booster shot questioning the strength of the data provided by J&J to support booster shots and stated that the FDA had not yet verified all of the available data. 
  • October 14, 2021: FDA’s VRBPAC recommends an EUA for Moderna boosters for elderly and at-risk populations six months after their second dose. Their recommendation includes individuals with frequent institutional or occupational exposure to COVID.
  • October 15, 2021: Despite noting that they had insufficient data just the day before, FDA’s VRBPAC recommended an EUA for J&J boosters to everyone 18 years of age and older who have already received the single-shot J&J vaccine at least two months after initial vaccination. The New York Times quotes VRBPAC members discussing a possible mix-and-match approach between booster types. Multiple scientists expressed concerns about possible confusion around the government’s recommendations.
  • October 20, 2021: FDA authorizes EUAs for Moderna and J&J boosters as well as mix-and-match boosters.
  • October 21, 2021: The CDC ACIP recommends Moderna and J&J boosters, as well as mix-and-match boosters.