The biggest obstacles to President Donald Trump’s order on vaccines may be the logistical challenges it poses for parents, health providers and drugmakers in the United States.

U.S. regulators have put the brakes on their push to speed Pfizer’s COVID-19 vaccine to children under 5.

Now, with the first vaccine rollouts and a surge in coronavirus infections, experts are debating what to do about the half that got a dummy shot. “There’s not an easy answer.”HOW VACCINE STUDIES WORKNew drugs, vaccines or treatments usually go through rigorous tests and evaluations before reaching regulators for approval. To do this fairly, researchers randomly assign participants to receive a vaccine or a dummy shot, usually a dose of salt water. On the flip side, if a person finds out they only received the dummy shot, they might take precautions they wouldn’t otherwise. Are we going to be happy with short-term evidence in a year?”WHAT THE COMPANIES SAYPfizer plans to eventually vaccinate all its study participants.

Moderna’s shot showed similarly strong effectiveness, providing 94% protection against COVID-19 in the company’s ongoing study of 30,000 people. Moderna’s vaccine uses the same groundbreaking technology as Pfizer-BioNTech’s shot. Both require two doses; Moderna's is four weeks apart. After the FDA acts, U.S. officials plan to move out an initial shipment of nearly 6 million Moderna doses. The government’s Operation Warp Speed program has orders for 200 million doses of Moderna’s vaccine.

Pfizer released no specific breakdowns, but for the vaccine to be 90% effective, nearly all the infections must have occurred in placebo recipients. REPORT 90% EFFECTIVE. But in July, Pfizer signed a contract to supply the U.S. with 100 million doses for $1.95 billion, assuming the vaccine is cleared by the FDA. Earlier this year, Fauci said he would be happy with a COVID-19 vaccine that was 60% effective. Pfizer has estimated it could have 50 million doses available globally by the end of 2020, enough for 25 million people.

Several drugs have proved useful and doctors know more about how to care for the sickest patients in hospitals, he said. People who have died from COVID-19, especially ones who took part in studies, have helped reveal what drugs do or do not help. Two anti-inflammatory drugs, one used in combination with remdesivir — the drug Wang helped test — also have been reported to help although results of those studies have not yet been published. In hospitals, doctors know more now about ways to avoid using breathing machines, such as keeping patients on their bellies. “Prevention is the most important step right now as we’re waiting for a vaccine and we’re improving treatment,” Goodman said.

A drug company says that adding an anti-inflammatory medicine to a drug already widely used for hospitalized COVID-19 patients shortens their time to recovery by an additional day. Eli Lilly announced the results Monday from a 1,000-person study sponsored by the U.S. National Institute of Allergy and Infectious Diseases. All study participants received remdesivir, a Gilead Sciences drug previously shown to reduce the time to recovery, defined as being well enough to leave the hospital, by four days on average. Those who also were given baricitinib recovered one day sooner than those given remdesivir alone, Lilly said. Lilly said it planned to discuss with regulators the possible emergency use of baricitinib for hospitalized COVID-19 patients.

University of Hong Kong scientists claim to have the first evidence of someone being reinfected with the virus that causes COVID-19. The man had mild symptoms the first time and none the second time; his more recent infection was detected through screening and testing at the Hong Kong airport. It shows that some people do not have lifelong immunity to the virus if they've already had it, To said. If there is a reinfection, it suggests the possibility there was residual immunity ... that helped protect the patient from getting sick again, Goodman said. ___The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institutes Department of Science Education.