Warning that fully vaccinated may be spreading Delta variant as cases rise across US

Health experts in the United States have raised the alarm that vaccinated individuals might be spreading the Covid-19 Delta variant, as cases surge in states across the country.

The highly transmissible Delta variant now makes up more than half of new infections in the US.

Currently the B.1.1.7, or Alpha, variant is the dominant strain in the country, But researchers said the Delta variant would likely overtake the Alpha variant in three to four weeks.

Christopher Murray, director of the Institute for Health Metrics and Evaluation, told Insider that the spread of the Delta variant could actually be worse than current data suggests.

“CDC guidance is not to test the vaccinated [unless they’re symptomatic], so we’re probably missing a bunch of transmission in vaccinated individuals,” Mr Murray said, who is the lead modeller at the IHME, which the White House has leaned on when making pandemic policies.

“We have 14 states where transmission has started to go back up,” he added.

The expert credited the rise in the Delta variant to both unvaccinated Americans and the relaxation of Covid-19 guidance across most of the US. The Centers for Disease Control and Prevention lifted its masking guidance in May for vaccinated Americans after more and more people received a jab.

But the spread of the Delta variant has influenced some areas across the US, such as Los Angeles County, to reimpose masking guidance for all residents, vaccinated or not.

Dr Ashish Jha, the dean of the Brown University School of Public Health, was another expert who pushed for Americans to consider re-masking regardless of their vaccination status.

“If you are fully vaccinated and encounter the Delta variant, you are about 90 per cent less likely to be infected than if you had not been vaccinated. And if you do get infected, you are extremely unlikely to get very sick. These facts underlie the CDC’s guidance that vaccinated people don’t need to wear masks indoors,” he wrote in an op-ed published in the Boston Globe.

But Dr Jha emphasised that 90 per cent does not give someone full protection, meaning that breakthrough infections and spreading of the virus to others could still occur.

“But here’s another way to see it: 90 per cent is not 100 per cent. And if a vaccinated person encounters the virus repeatedly or in high enough concentrations, the chances of a breakthrough infection gets more substantial,” he said.

States with low vaccination rates have reported higher rates of infections and hospitalisations, fuelling the spread of the Delta variant.

Missouri, for example, reported that 96 per cent of its new Covid-19 cases were because of the Delta variant as of Tuesday, according to data compiled by Scripps Research’s Outbreak.info. This comes as just 39.4 per cent of the population was fully vaccinated against the novel virus.

Arkansas was another state experiencing a surge in Covid-19 cases, as just 34.6 per cent of the population was fully vaccinated.

In comparison, 47.6 per cent of all US residents were fully vaccinated.

Dr Anthony Fauci encouraged vaccinated residents to wear a mask in areas with high transmission and low vaccination rates to protect themselves as these new variants spread.

“If you put yourself in an environment in which you have a high level of viral dynamics and a very low level of vaccine you might want to go the extra step and say, ‘When I’m in that area where there’s a considerable degree of viral circulation, I might want to go the extra mile, to be cautious enough to make sure that I get the extra added level of protection even though the vaccines themselves are highly effective,’” Dr Facui said on NBC’s Meet the Press Sunday.

Early research has indicated the Delta variant might impact vaccine effectiveness.

A study conducted of Pfizer’s vaccine in Israel, which has not been peer reviewed, found that the vaccine protected 64 per cent of people from infection amid the Delta variant outbreak, which was down from the 94 per cent of people previously protected.

The vaccine was still effective in preventing severe disease and hospitalisation, though, with a 94 per cent effectiveness rate.

Health experts have been wary towards the report from Israel’s Health Ministry given the study’s authors failed to provide how they conducted the research and who participated.