COVID-19 vaccine trials provide rush of good news as cases mount
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Just 10 months after scientists in China shared the genetic sequence of the SARS-CoV-2 virus, several drug makers readied submissions to the FDA asking for emergency use authorizations for their COVID-19 vaccines.
A rush of positive late-stage trial results came as cases and deaths spiked around the world, and most U.S. states dealt with uncontrolled outbreaks.
As the data and regulatory submissions stacked up, the CDC’s Advisory Committee on Immunization Practices held an emergency meeting to vote on how initial supplies of COVID-19 vaccines would be allocated and recommended in a 13-1 vote that health care personnel and residents in long-term care facilities be prioritized.
“Initial doses of any COVID-19 vaccine will be limited,” Sara E. Oliver, MD, MSPH, an Epidemic Intelligence Service officer in the CDC’s Division of Viral Diseases, said during the meeting. “We expect a constrained supply environment for some months and need to make the best use of available vaccine.”
Record speed
The speed of the vaccine trials was unprecedented. From start to finish, the record for vaccine development had been 4 years, for the mumps vaccine. National Institute of Allergy and Infectious Diseases Director Anthony S. Fauci, MD, called the quick pace of COVID-19 vaccine development and the resulting data showing their effectiveness “extraordinary.” In comments during a White House Coronavirus Task Force briefing, Fauci noted that 95% efficacy “is almost to the level of what we see with measles.”
“That’s what we’re dealing with,” he said.
Surveys have suggested that many Americans will be hesitant to receive a COVID-19 vaccine, despite the seriousness of the pandemic. Fauci said he wanted to settle any concern that the vaccine programs moved too fast “to put to rest any concept that this was rushed in an inappropriate way.”
“Speed did not compromise at all safety, nor did it compromise scientific integrity,” Fauci said. “It was a reflection of the extraordinary scientific advances in these types of vaccines, which allowed us to do things in months that actually took years before.”
‘Great news’
On Nov. 9, Pfizer and BioNTech announced that their two-dose messenger RNA (mRNA)-based vaccine candidate was highly efficacious in preventing COVID-19 and showed no serious safety concerns in an interim analysis of phase 3 clinical trial results — the first of several successive positive announcements made over a few weeks by vaccine manufacturers.
“This is great news,” Florian Krammer, PhD, a professor of vaccinology at the Icahn School of Medicine at Mount Sinai in New York, told Infectious Disease News. “There are many open questions, but we now might have a tool to mitigate the effects of this pandemic.”
A final analysis of the of the phase 3 data revealed that the vaccine was 95% efficacious against COVID-19 beginning 28 days after the first dose with no serious safety concerns. The estimate was based on 170 confirmed cases of COVID-19 among trial participants — 162 in the placebo arm and eight in the treatment arm. According to the companies, 10 of the cases of COVID-19 among trial participants were severe — nine of them in the placebo group.
In announcing their submission for an emergency use authorization (EUA), the companies said 50 million doses of the vaccine would be available globally by the end of the year, enough to vaccinate up to 25 million people. They said 1.3 billion doses could be available by the end of 2021.
The vaccine, which must be stored at nearly –100°F, will be moved in specially designed, temperature-controlled shippers equipped to maintain extremely cold temperatures, the companies said. Once delivered, doses can be stored at normal refrigerated temperatures for up to 5 days.
Another two-dose mRNA-based vaccine co-developed by Moderna and the NIH was shown to be 94.1% efficacious overall and 100% efficacious against severe COVID-19, with no serious safety concerns identified to date, according to preliminary data.
The analysis included 196 COVID-19 cases, of which 185 occurred in the placebo group and 11 in the treatment arm. All 30 severe cases of COVID-19 occurred in the placebo arm, Moderna said.
The company said it would have approximately 20 million doses of its vaccine ready to ship in the U.S. by the end of 2020 and up to 1 billion doses available globally in 2021. It also said that new data indicate the vaccine remains stable for 30 days at 36°F to 46°F, which could mitigate issues related to cold shipment and storage and make distribution easier.
A third vaccine, co-developed by AstraZeneca and Oxford University, was an average of 70% efficacious using two different dosing schedules, according to pooled data from trials in the United Kingdom and Brazil.
The vaccine was 90% efficacious when given as a half dose, followed by a full dose at least 1 month apart — an unintended schedule that was the result of a manufacturing error in which some trial participants received a half dose by mistake, Oxford said. The other dosing regimen was 62% efficacious when given as two full doses at least 1 month apart, AstraZeneca reported. The company said there have been no serious safety events related to the vaccine.
In contrast to the mRNA-based vaccines, the AstraZeneca/Oxford vaccine is a chimpanzee adenovirus-vectored vaccine. It is stable at normal refrigerated temperatures for at least 6 months. The company said it has the capacity to produce up to 3 billion doses in 2021.
“I think by the middle of next year we’ll have at least a half-dozen promising COVID-19 vaccines,” Peter J. Hotez, MD, PhD, FASTMH, FAAP, dean of the National School of Tropical Medicine at Baylor College of Medicine and co-director of the Center for Vaccine Development at Texas Children’s Hospital, told Infectious Disease News. “It may turn out that the spike protein of the SARS-CoV-2 is a relatively ‘soft target’ in terms of the effects of inducing virus-neutralizing antibodies.”
One remaining question is how long immunity from these vaccines will last. Krammer said “there is no reason to believe it will disappear quickly.”
“We will find out once time goes by,” he said.
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