(CN) — The World Health Organization on Tuesday said the bumpy rollout of vaccines around the world against the novel coronavirus was to be expected for an endeavor so complex and unprecedented.
Separately, the United Nations health agency also said during a news briefing that it was “disappointed” that China on Tuesday blocked the arrival of an international team of experts looking into the origins of the novel coronavirus. The agency's chief said he was hopeful China would soon allow the team in.
Around the world, more than 30 nations have begun vaccination programs but there are growing concerns over how well vaccines are being used, approved and distributed.
In Europe, politicians are under fire for a slow rollout of vaccines. India and China are pushing ahead with mass inoculation programs after approving vaccines that experts worry haven't been fully vetted. In the United Kingdom, faced with an explosive outbreak and a shortage of vaccines, the government has chosen to give people a first vaccine jab to make them somewhat immune and delay when they get a second booster shot.
“I think we're seeing those growing pains,” said Dr. Kate O'Brien, the head of the WHO's program for immunization, vaccines and biologicals. “We're starting to see where some of those road bumps are and where we need to make adjustments.”
WHO experts said getting the new vaccines against coronavirus distributed and into people's arms will be extremely difficult.
“This is a complex process, it is resource intensive – both human and physical and financial resource intensive,” said Dr. Mike Ryan, the head of emergencies at WHO.
He said many countries underestimated how difficult setting up new mass vaccination programs would be and that they now need to invest in their health systems to handle this new burden.
“All countries need to really take a hard look at their capacity to deliver vaccines,” he said.
He added that it's not good enough for nations to simply secure vaccines but also track who gets inoculated.
“You can't file and forget, you can't dispatch and forget; you have to follow each vaccine right into the arm of the person who has to get it,” Ryan said. “You've got to follow that chain.”
In the European Union, there is frustration over a slow rollout of vaccines in some nations, most notably France, where only about 500 people have been inoculated so far. In all, the EU has vaccinated about 500,000 people since it approved the use of the Pfizer-BioNTech vaccine shortly before Christmas. By comparison, more than 1 million people have received shots in the United Kingdom and more than 4 million in the United States.
The EU was slower than both the U.K. and U.S. to approve the Pfizer-BioNTech vaccine for emergency use. Last week, the WHO also gave its approval for the Pfizer-BioNTech vaccine. Clinical trials showed the vaccine being highly effective against the coronavirus, but it must be stored at ultra-cold temperatures and this has proven to be difficult and expensive.

In the U.K. and the U.S., a scientific debate has erupted over whether it's prudent to delay giving people a second booster shot of two highly touted vaccines, the Pfizer-BioNTech and Moderna antidotes, which are based on providing immunity through a new method using RNA, a type of molecule found in human cells. By delaying a second shot, more people can be vaccinated, though it's unclear how effective a single dose is against infection. The Pfizer-BioNTech makers say a second dose should be administered 21 days after the first one but Britain is now telling people who get the first dose that they will have to wait up to 12 weeks for the second shot.