The World Health Organization's top vaccine expert says the agency needs to evaluate coronavirus vaccines and their immune responses based on more than just a press release.

Kate O'Brien, WHO's director of immunization, vaccines and biologicals, said at a press briefing in Geneva on Friday that it was still not clear if vaccines against COVID-19 were able to reduce people's ability to spread the virus.

"It's really important that we actually start to get more information about what the vaccines do, not just for preventing disease, but for actually preventing the acquisition of the virus," O'Brien said.

British drugmaker AstraZeneca said Thursday that it was cooperating with government regulators in investigating a manufacturing error in an experimental COVID-19 vaccine.

The pharmaceutical company and Oxford University have admitted that a lower dose of the vaccine performed better than a full dose, according to a spokesman who spoke after AstraZeneca's CEO said a further global trial was likely.

The statement came as the company prepared to provide a temporary supply of the drug ahead of its plans to distribute 4 million doses of the vaccine by the year's end.

The England-based pharmaceutical company said earlier this week that its vaccine was 70% effective overall, but there were differences between two dosing regimens. One was 90% effective. The other was 62%.

Drugmakers Pfizer and Moderna have also announced initial results from late-stage trials showing their vaccines were nearly 95% effective.

Meanwhile, in the United States, where the number of coronavirus cases neared 13 million, according to the Johns Hopkins Coronavirus Resource Center, the pandemic kept crowds small at stores across the country on Black Friday. Many stores were relying on online shopping and curbside pickup options for sales.

The number of COVID-19 patients being treated in hospitals across the United States reached 90,000 on Friday after nearly doubling in the last month, according to the Reuters news agency. The hospitalizations came after weeks of rising infection rates in the United States and have increased worries that Thanksgiving gatherings this week with family and friends would lead to even more infections and hospitalizations.  

In Ireland, the government said it would allow shops, restaurants and gyms to reopen next week after the latest round of shutdowns. Prime Minister Micheal Martin said travel would be permitted between counties in the week preceding Christmas.

"We now have the opportunity to enjoy a different but special Christmas," he said in a televised address.

Officials in France said the rate of new coronavirus infections slowed again Friday, as the country prepared to allow for the reopening Saturday of stores selling nonessential goods.

Italy is also seeing a gradual decline in hospitalizations from the coronavirus, leading the government to announce that it would ease restrictions in five regions from Sunday, including the populous Lombardy region.

The number of coronavirus infections in Germany topped 1 million on Friday. The country's disease control center, the Robert Koch Institute, reported 22,806 cases overnight, bringing the country's total since the start of the outbreak to more than 1 million.

Iran on Friday announced that its government offices would operate only with essential staff because of a surge in coronavirus cases. Officials reported a record number of new cases on Friday - 14,051 - bringing the country's total to more than 922,000.

In other developments, Australia's second-largest state, Victoria, has recorded no new coronavirus infections or deaths in the past 28 days, health officials said Friday.

The state did not have any active cases after the last COVID-19 patient was discharged from the hospital Monday. 

While Victoria has achieved the 28-day benchmark, widely accepted by health experts as eliminating the virus from the community, cases of coronavirus infections have been detected in other parts of the country.

In Latin America, Brazilian President Jair Bolsonaro said Thursday that he would refuse a coronavirus vaccine, the most recent of his vaccine-skeptic statements.    

"I'm telling you, I'm not going to take it. It's my right," he said in remarks aired over several social media platforms.

Brazil, with more than 6.2 million cases of COVID-19, is behind only the United States and India, and at more than 171,000 deaths, it is behind only the United States, according to Johns Hopkins.