LONDON — Europe is slipping behind in its vaccination drive and could see hundreds of thousands more deaths by next spring, the World Health Organization has said.

Robb Butler, WHO Europe’s executive director, said to CNBC that only 54% of Europe’s one billion inhabitants have been vaccinated.

For the U.N., this area includes 53 countries. This actually covers Europe and Central Asia. 900,000 citizens at its last count.

“There are [around] 45% who are unvaccinated or not fully vaccinated, that’s a bigger issue for our policy and decision-makers right now — driving up vaccination rates,” he told CNBC’s “Squawk Box Europe” on Wednesday.

Butler’s remarks come at a time when Europe is struggling with the latest Covid infection wave, prompting more restrictive measures and driving hospitalizations up.

According to health officials in the region, most, if not all of those who were admitted to intensive care units with Covid have never been vaccinated. While Covid vaccines do not prevent transmission, they can reduce severe infections and the possibility of death.

WHO Europe warned Tuesday that the large number of people who have not been vaccinated puts them at high risk for excessive deaths over the next months. The WHO issued a statement in which it stated: the Covid death toll in Europe and Central Asia could rise by 700,000 to reach more than 2.2 million by next March.

According to WHO, 1.5 million Covid-related deaths have already been recorded in Europe. The virus is now the number one cause of death for both Europe and Central Asia.

According to the statement, nearly 4200 people die in the region each day. This is twice as many deaths than the September end.

WHO consistently stated that Europe is the epicenter of Covid infection. There are many differences in vaccination rates between countries, for both the booster shots as well as initial Covid vaccinations.

Germany may tighten its Covid regulations, which could mean lockdown measures. A decision is expected Wednesday. As the number of infections rises, Spain tightens its controls. Austria wants total lockdown, while the Netherlands prefers a partial.

Austria will become the first country in Europe to mandate Covid vaccines starting February 2019. However, there has been some pressure from other countries to do so.

Butler from WHO said that the agency does not hold a position on mandates, but stated they were “very delicate”.

It polarizes and you run the risk of marginalizing [people]It can also be detrimental to trust and inclusion. It’s not a good idea, and it is a last resort measure. We have learned from the past that vaccines can cause trust erosion and polarization.

Ursula von der Leyen (President of European Commission) called for Tuesday’s deployment booster shots. She also stated other preventive measures needed to lower infection rates.

To stop or slow down the spread of the virus, further measures must be taken. Social distancing, mask wearing, hygiene rules, etc. are some of the key measures. These are all equally important. It is becoming increasingly difficult for many people, and I am sure that we cannot forget about something. “In the EU, 1,600 people are killed every day by Covid. 1,600 people each day, day after daily,” she said.

She added that vaccinations and other hygiene measures were an act of solidarity and can save lives.

—CNBC’s Robert Towey contributed reporting to this story.