New infections and deaths from HIV/AIDS may increase as the Covid-19 pandemic has disrupted prevention measures, said UNAIDS Executive Director Winnie Byanyima in an interview airing on Wednesday at the Reuters Next conference.

Byanyima, who is also United Nations under-secretary-general, said that during the first pandemic phase in particular, fewer people opted to be tested and some dropped out of treatment because of long lines at clinics or other public safety measures that impeded access to prevention measures.

"We do expect that in the coming years, we might see more deaths, we might see more new infections as a result of these disruptions," she said in the pre-recorded interview that aired on World AIDS Day.

Byanyima said vaccine nationalism, in which rich countries buy up vaccine supplies and poor nations are left waiting, has been "among the saddest part of where we are."

As rich countries have hoarded vaccines, just over 7% of Africa's population has been fully vaccinated, according to the Our World in Data project at the University of Oxford.

Some scientists believe that might have been a factor in the development of Omicron, the new variant first discovered in southern Africa that has prompted alarm over chances that vaccines might not be effective against it.

"It is no coincidence to most of us that it arose in Sub Saharan Africa, where you have a lot of under-diagnosed HIV infections, or people who are immunocompromised with it," said John Moore, a professor of microbiology and immunology at Weill Cornell Medical College in New York, in a separate interview.

Moore said people who are immunocompromised cannot clear the infection as quickly as those with healthy immune systems, and that a suboptimal immune response can allow the virus to keep mutating.

"That's how the other variants are thought to have arisen - in immunocompromised people," he said.

Byanyima said research shows that people with HIV are no more likely than others to become infected with SARS-CoV-2, the virus that causes Covid-19, but that once infected, they are at much higher risk of severe illness.

"That is why for developing countries with a high burden of HIV, this is critical," she said of the access to Covid-19 vaccines.