Pfizer Covid-19 vaccine 'very promising' but has cold chain issues: WHO

The World Health Organization's (WHO) chief said on Tuesday it hopes to have a Covid-19 vaccine by year-end and that Pfizer's experimental remedy is "a very promising one", with more expected.

But the vaccine, based on a novel technology that uses synthetic mRNA to activate the immune system against the virus, comes with special challenges as it needs to be stored at minus 70 degrees Celsius (-94 F) or below - equivalent to an Antarctic winter.

WHO Director-General Tedros Adhanom Ghebreyesus reiterated the United Nations agency's call for an equitable distribution of vaccine doses once they are available.

Pfizer said on