There will be no "herd immunity" to COVID anywhere this year, the World Health Organization says.

Vaccinations against COVID-19 began only recently, the organization said Monday.

Its chief scientist Dr. Soumya Swaminathan Yadav said it would take some time to build immunity to the virus.

In the meantime she encouraged people to continue strict social distancing measures for the rest of the year, wear face masks and wash their hands often.

"Even as vaccines start protecting the most vulnerable, we're not going to achieve any levels of population immunity or herd immunity in 2021," Swaminathan said. "Even if it happens in a couple of pockets in a few countries it's not going to protect people across the world."

Herd immunity takes years and demands the inoculation of half to more than 80% of a country's population. The organization defines herd immunity, also known as population immunity, as the indirect protection from an infectious disease that occurs when a population is immune either through vaccinations or immunity developed through a previous infection.

The organization supports achieving herd immunity through vaccinations and not by allowing a disease to spread in any segment of the population - that results in unnecessary cases and deaths.

The organization is sure herd immunity against COVID should be achieved by vaccinations.

It said that for the world to achieve herd immunity a substantial percentage of a population must be vaccinated - lowering the overall amount of virus able to spread in the whole population.

"The vaccines are going to come," Swaminathan said. "They are going to go to all countries...but meanwhile we mustn't forget that there are [public health] measures that work."

It takes time to produce and administer enough doses of a vaccine to stop the spread of COVID. Swaminathan emphasized the need for countries to continue with the proven social protocols and hygiene.