Covid cases are on the rise in some 110 countries, driven by the BA.4 and BA.5 variants, amounting to a 20 percent spike overall, and a rise in the number of deaths across three of the six world regions monitored by the World Health Organization, the UN health agency chief has said.

The global figure overall remains relatively stable, but nobody should be under any illusion that the coronavirus is on the way out, WHO Director-General Tedros Adhanom Ghebreyesus said Wednesday.

"This pandemic is changing but it's not over. We have made progress but it's not over, he added. "Our ability to track the virus is under threat as reporting and genomic sequences are declining. The optimistic mid-year deadline for all countries to vaccinate at least 70 percent of their populations is looking unlikely, with the average rate in low-income countries, standing at 13 percent."

However, in the past 18 months, more than 12 billion vaccines were distributed around the world, and 75 percent of the world's health workers and over-60s are now vaccinated.

The influential Lancet medical journal estimates that 20 million lives were saved because of vaccines, Tedros said.

Read: Bangladesh reports no death from Covid-19, new cases 56

Last year, it was the hoarding of vaccines by rich and manufacturing countries which proved to be the major barrier to access, but this year, it is what he described as the wavering "political commitment to getting vaccines out to people and challenges of disinformation," which is thwarting the pace of inoculations at the national level.