Several more drug manufacturers have joined the global effort to develop a coronavirus vaccine.
However, experts remain unconvinced a vaccine proven to be safe and effective will be available this calendar year.
"I think we'll have to have one more cycle of this virus in the fall, heading into the winter, before we get to a vaccine," Dr. Scott Gottlieb, former head of the Food and Drug Administration, told CNBC this week.
"I really think a vaccine is probably a 2021 event, in terms of having wide availability of a vaccine for the general population."
Here is a roundup of the most notable vaccine news of the week.
Merck begins studies of 2 vaccine candidates
Drug giant Merck announced this week that it's investigating two potential COVID-19 vaccines.
The first is from Themis, a Vienna-based company that Merck has acquired. The Themis candidate is based on a previously developed vaccine that contains a weakened version of the measles virus. Scientists are adding bits of the coronavirus to the vaccine in an effort to teach the body's immune system to recognize the virus.
"We are eager to combine our strengths both to develop an effective COVID-19 vaccine in the near term and to build a pandemic preparedness capability directed toward emerging agents that pose a future epidemic threat," Dr. Roger Perlmutter, president of Merck Research Laboratories, said in a statement.
Studies for safety and efficacy in humans could begin in the next month or so.
Merck is also partnering with the nonprofit scientific research organization IAVI to re-engineer an existing vaccine for Ebola. Clinical trials are expected to begin this year.
Novartis tries gene-based approach
Also this week, Novartis announced it plans to make a gene-based coronavirus vaccine, which is in development at the Massachusetts Eye and Ear hospital, the Massachusetts General Hospital and the University of Pennsylvania.
A subsidiary of Novartis called AveXis would manufacture the vaccine.
"The COVID-19 pandemic is the most urgent public health crisis of our time and we recognize the significance of evaluating the potential role of a gene-based vaccine," AveXis President Dave Lennon said in a statement.
The approach uses an inactive form of the coronavirus to deliver the virus's DNA into the body, teaching it to make proteins found on the surface of coronavirus particles. Those proteins are the spikes seen on microscopic images of the virus. (The coronavirus gets its name from the crown-like spikes on its surface. "Corona" is Latin for "crown.")
Manufacturing is expected to begin this month, and clinical trials could start later this year.
Early Novavax results expected soon
The Maryland-based biotechnology company Novavax said it's launched preliminary clinical trials of its coronavirus vaccine candidate. The first results, on whether the drug is safe and effective, could be released as soon as July.
The company aims to provide vaccines for those on the front lines of the COVID-19 pandemic: health care workers.
"If our phase two data support the safety and immunogenicity that we hope it will and we're able to see a signal for efficacy, it's possible that that first line would be vaccinated sometime in the fourth quarter of this year," Stanley Erck, CEO of Novavax told CNBC.
If they build it, will you roll up your sleeve?
As scientists worldwide scramble to develop a vaccine for the virus that's killed more than 350,000 people globally in just five months, a poll from the Associated Press-NORC Center for Public Affairs Research finds many Americans would refuse the shot.
About half of the more than 1,000 people surveyed in the U.S. said they would get a vaccine for the coronavirus.
Nearly a third were unsure whether they'd get it. Another 1 in 5 said they would refuse such a shot.
Older adults, who tend to be most vulnerable to COVID-19, were more likely than younger adults to say they'd get the vaccine. Sixty-seven percent of those over age 60, compared to 40 percent of younger people, confirmed they would be willing to be vaccinated.
Many are counting on the vaccine to get back to normal life. About 7 in 10 of those surveyed who said they would get the vaccine said it was necessary before lifting all restrictions.