A spokesman for the chairman of the Senate committee, Senator Ron Johnson, Republican of Wisconsin, did not immediately return an email message asking why Dr. Orient had been invited to testify.
Federal health officials are trying to enlist lawmakers in a campaign to encourage Americans to accept the new vaccines. An F.D.A. advisory committee will meet on Thursday to review data on the safety and efficacy of Pfizer’s vaccine candidate. If the agency grants the vaccine emergency authorization, rollout could begin shortly after.
In a private briefing with a bipartisan group of senators last month, Moncef Slaoui, the chief scientific adviser to Operation Warp Speed, the Trump administration’s vaccine development program, said that “it would help if senators got vaccinated,” according to a person familiar with the call.
Dr. Orient, who lives in Tucson, Ariz., said on Sunday that she would appear remotely during the hearing on early at-home treatment for Covid-19. Her group has been a forceful proponent of at-home treatment, the ostensible subject of the committee hearing.
The association has also sued the government in an effort to force it to release hydroxychloroquine from the national stockpile for use as a Covid-19 treatment, although the scientific evidence indicates that the drug is ineffective against the coronavirus. The case is currently before a federal appeals court.
Dr. Orient said she intended to use her testimony to call for government guidelines informing doctors about hydroxychloroquine as a potential treatment for Covid-19 patients, even though the Food and Drug Administration revoked an emergency authorization allowing the drug to be distributed from the national stockpile and has warned that it could harm those patients.
Dr. Orient’s organization has urged people to be cautious about the vaccine in blog posts with titles like “Should We Line Up for a 90% Effective Vaccine?” In her interview, she raised particular concerns about vaccinations for young people “because the effect on fertility has not been determined.” There is no evidence that any of the leading coronavirus vaccines affect fertility.
Dr. Orient also took aim at Dr. Anthony S. Fauci, the government’s top infectious disease specialist, asking, “Why is he dictating care for 340 million Americans?”