“So very quickly, we start having more than 150 million doses a month in March, April, May,” he added. He and other federal officials have said that the general public is likely to be able to be vaccinated by May or June.
Confused by the all technical terms used to describe how vaccines work and are investigated? Let us help:
- Adverse event: A health problem that crops up in volunteers in a clinical trial of a vaccine or a drug. An adverse event isn’t always caused by the treatment tested in the trial.
- Antibody: A protein produced by the immune system that can attach to a pathogen such as the coronavirus and stop it from infecting cells.
- Approval, licensure and emergency use authorization: Drugs, vaccines and medical devices cannot be sold in the United States without gaining approval from the Food and Drug Administration, also known as licensure. After a company submits the results of clinical trials to the F.D.A. for consideration, the agency decides whether the product is safe and effective, a process that generally takes many months. If the country is facing an emergency — like a pandemic — a company may apply instead for an emergency use authorization, which can be granted considerably faster.
- Background rate: How often a health problem, known as an adverse event, arises in the general population. To determine if a vaccine or a drug is safe, researchers compare the rate of adverse events in a trial to the background rate.
- Efficacy: A measurement of how effective a treatment was in a clinical trial. To test a coronavirus vaccine, for instance, researchers compare how many people in the vaccinated and placebo groups get Covid-19. The real-world effectiveness of a vaccine may turn out to be different from its efficacy in a trial.
- Phase 1, 2, and 3 trials: Clinical trials typically take place in three stages. Phase 1 trials usually involve a few dozen people and are designed to observe whether a vaccine or drug is safe. Phase 2 trials, involving hundreds of people, allow researchers to try out different doses and gather more measurements about the vaccine’s effects on the immune system. Phase 3 trials, involving thousands or tens of thousands of volunteers, determine the safety and efficacy of the vaccine or drug by waiting to see how many people are protected from the disease it’s designed to fight.
- Placebo: A substance that has no therapeutic effect, often used in a clinical trial. To see if a vaccine can prevent Covid-19, for example, researchers may inject the vaccine into half of their volunteers, while the other half get a placebo of salt water. They can then compare how many people in each group get infected.
- Post-market surveillance: The monitoring that takes place after a vaccine or drug has been approved and is regularly prescribed by doctors. This surveillance typically confirms that the treatment is safe. On rare occasions, it detects side effects in certain groups of people that were missed during clinical trials.
- Preclinical research: Studies that take place before the start of a clinical trial, typically involving experiments where a treatment is tested on cells or in animals.
- Viral vector vaccines: A type of vaccine that uses a harmless virus to chauffeur immune-system-stimulating ingredients into the human body. Viral vectors are used in several experimental Covid-19 vaccines, including those developed by AstraZeneca and Johnson & Johnson. Both of these companies are using a common cold virus called an adenovirus as their vector. The adenovirus carries coronavirus genes.
- Trial protocol: A series of procedures to be carried out during a clinical trial.
The C.D.C. panel was originally not supposed to vote on its recommendations until after the F.D.A. had approved a vaccine. But it bumped up the timing to give states more guidance as they complete their distribution plans, which must be submitted to the C.D.C. on Friday.
On Tuesday, the group specifically suggested that within the long-term-care population, residents of nursing homes, who tend to be the most frail and susceptible to Covid, should get the first vaccines in the event that there aren’t enough, along with staff members who have not had the virus within the last 90 days.
Within the much larger category of health care workers, the panel said that health systems should consider prioritizing those who have direct contact with patients and their families and those who handle infectious materials. Dr. Nancy Messonnier, who leads the C.D.C.’s National Center for Immunization and Respiratory Diseases, told the panel that based on her recent conversations with state health officials, most states and large cities “believe they can vaccinate all of their health care workers within three weeks.”
But whether they reach that goal depends on how much vaccine they get, and how quickly. Gov. Andy Beshear of Kentucky told reporters on Monday that his state had more than 200,000 health care workers but would receive only 38,000 doses in its first shipment and that it might not get another for two weeks.
Long-term-care facilities include nursing homes, with about 1.3 million residents; assisted-living facilities, with 800,000 residents; and residential care facilities, which tend to be small and cater to specific populations. The federal government has contracted with CVS and Walgreens to deliver vaccines to most such facilities nationwide, with teams of pharmacists making three visits to each to ensure that every staff member and resident gets both an initial shot and a booster shot several weeks later.
Several members of the panel urged that small community doctors’ offices not be left off the initial priority list. “Transmission dynamics suggest providers who care for patients earlier in their course of illness may be at higher risk,” said Dr. Jeffrey Duchin, a member of the panel who is in charge of public health in Seattle and King County, Wash.