Dr. Anthony Fauci, US President Joe Biden’s chief medical adviser, commented on Monday about the “breakthrough infections”, in which people who are fully vaccinated against COVID-19 contract the virus.

Speaking at a press briefing of the COVID-19 response team, Fauci said that as of July 26 the CDC had received 6,587 reports of breakthrough infections that resulted in hospitalizations or deaths out of 163 million fully vaccinated Americans.

“No vaccine is 100% effective, so you can expect breakthrough infections. Most of these infections are going to be asymptomatic or mild,” he explained.

Fauci added that people who have been infected should still get the vaccine in order to add a stronger layer of protection, noting the delta variant is producing more reinfections.

“The protection you get from the original infection still exists somewhat, but reinfections occur at a much greater rate among individuals now than they did against the original (strain),” he said.

“The recommendation still holds that even though you've been infected previously in the context of variants, it's a good idea to get vaccinated anyway," added Fauci.

Earlier on Monday, US Senator Lindsey Graham (R-SC) announced that he had tested positive for COVID-19 even after being vaccinated.

"I feel like I have a sinus infection and at present time I have mild symptoms. I will be quarantining for ten days. I am very glad I was vaccinated because without vaccination I am certain I would not feel as well as I do now. My symptoms would be far worse," he tweeted.