Individuals who have not been vaccinated against the coronavirus disease (COVID-19) do not only risk their own health but are potential "variant factories," experts said.

"Unvaccinated people are potential variant factories. The more unvaccinated people there are, the more opportunities for the virus to multiply," Dr William Schaffner, a professor in the Division of Infectious Diseases at Vanderbilt University Medical Center, told CNN.

He warned that populations of unvaccinated people give the virus the chance not only to spread but also to change.

"When it does, it mutates, and it could throw off a variant mutation that is even more serious down the road."

Andrew Pekosz, a microbiologist and immunologist at the Johns Hopkins Bloomberg School of Public Health, explained that as mutations come up in viruses, the ones that persist are the ones that make it easier for the virus to spread in the population.

"Every time the viruses changes, that gives the virus a different platform to add more mutations. Now we have viruses that spread more efficiently," he told CNN.

The are already several variants of the coronavirus around the world including the the B.1.1.7 or Alpha variant that was first seen in England, the B.1.351 or Beta variant first spotted in South Africa, and the Delta variant or B.1.617.2 first detected in India.

The World Health Organization had earlier advised that "the more we allow the virus to spread, the more opportunity the virus has to change."

"Every time we see the virus circulating in the population, particularly a population that has pockets of immune people, vaccinated people, and pockets of unvaccinated people, you have a situation where the virus can probe," Pekosz added.

In the United States, only 18 states have fully vaccinated more than half their residents, according to data from the US Centers for Disease Control and Prevention.

As of June 27, the Philippines has so far recorded a total of 2,527,286 Filipinos who have been fully vaccinated against the virus.