More Covid-19 vaccines are being developed by researchers in the United States than in any other country, according to the WHO.
The WHO's most recent update on global vaccine development projects, published Tuesday, showed there are currently at least 133 vaccines being tested around the world.
U.S. institutions are working on the highest number of these — 42 — according to the WHO's list, and Chinese research facilities are working on 19, meaning China is developing the second-highest number of vaccines.
Of the 133 vaccines, 10 vaccines are in the clinical trial phase (meaning they are being tested on human volunteers) and 123 vaccines are in the preclinical trial phase.
China is working on more projects in the clinical trial phase than any other country, with the U.S. following close behind.
Projects that have progressed to clinical trials include Moderna's potential vaccine, which the U.S. company said generated some positive data in early tests last month. However, vaccine experts later expressed skepticism about the company's data. The firm's chairman told CNBC that it would never put out data on its vaccine that varied from "reality."
Another vaccine undergoing human trials is being developed at Oxford University in England, which pharmaceutical giant AstraZeneca has agreed to manufacture and distribute at cost. The project, which aims to roll out 30 million doses of the immunization in the U.K. within months if successful, recently received $1 billion in U.S. government funding.
At least 123 further potential vaccines are being investigated around the world, according to the WHO, but these are in the earlier "preclinical evaluation" phase of trials — meaning they may never be tested on humans.
A number of the projects listed by the WHO are cross-border collaborations, meaning researchers in more than one country are contributing.
Regionally, Europe has the most Covid-19 vaccines in development, with experts at 56 European institutions looking for potential immunizations. There are 54 vaccine projects being conducted across North America, and 25 vaccines being researched in the Asia-Pacific region, according to the WHO's data.
Despite hundreds of scientists looking for a vaccine for the new coronavirus, however, experts have warned that an effective immunization for Covid-19 may never be found. Many have also warned that any successful vaccine would take around 12 to 18 months to be safely rolled out to the market.
Experts have also warned that even if an effective vaccine becomes available, significant logistical challenges will remain around distributing enough doses for the global population.