An exterior view of the headquarters of the World Health Organization (WHO) in Geneva. (Xinhua/Liu Qu)

Scientists at the World Health Organization (WHO) warned that mass vaccinations would not bring about herd immunity to the coronavirus this year, even as one leading producer boosted its production forecast.

Infections numbers are surging around the world, especially in Europe where nations have been forced to ramp up virus restrictions even as vaccines are rolled out.

The WHO's chief scientist Soumya Swaminathan warned Monday that it would take time to produce and give enough shots to halt the spread of the virus, which has infected more than 90 million people worldwide with deaths approaching 2 million.

"We are not going to achieve any levels of population immunity or herd immunity in 2021," she said, stressing the need to maintain physical distancing, hand-washing and mask-wearing.

Experts are also concerned about the rapid spread of new variants of the virus, such as the one first detected in Britain which is feared to be significantly more transmissible.

England opened seven mass vaccination sites Monday to fight a surge fueled by that variant, which is threatening to overwhelm hospitals.

But England's chief medical officer Chris Whitty told the BBC, "The next few weeks are going to be the worst weeks of this pandemic in terms of numbers into the NHS (National Health Service)."

Elsewhere in Europe, Portugal was facing a new lockdown because of a spike in cases and deaths, as the President Marcelo Rebelo de Sousa tested positive for the virus.

Germany's BioNTech, which partnered with Pfizer to produce the first vaccine approved in the West, said it could produce millions more doses than originally expected this year, boosting the production forecast from 1.3 to 2 ­billion.

The announcement was a boost to countries struggling to deliver the shots, but the company also warned that Covid-19 would "likely become an endemic disease," with vaccines needed to fight new variants and a "naturally waning immune response."

Officials in Russia said they would trial a one-dose version of country's Sputnik V vaccine as part of efforts to provide a stopgap solution for badly hit countries.

India, with the world's second-highest number of infections, is set to begin giving shots to its 1.3 billion people from Saturday in a colossal and complex undertaking.

Malaysia's king declared a nationwide state of emergency Tuesday to fight a coronavirus surge that is overwhelming hospitals.