Millions of Johnson & Johnson vaccines are set to expire in June, and thousands could be wasted because fewer and fewer Americans are getting vaccinated, according to reports by The Wall Street Journal and The New York Times.

Some states have considered shipping excess doses to other states or even overseas, but said they faced legal and logistical hurdles.

The J&J vaccine is easier to transport, store, and administer than other vaccines. Johnson & Johnson's vaccine is the only single-dose vaccine authorised in the US, and can also be stored in a regular refrigerator for up to three months. But public opinion of the jab has soured, following reports that it could cause blood clots in very rare cases, and that a factory in Baltimore producing the vaccine ruined up to 15 million doses and failed to meet sanitation protocols.

As the Food and Drug Administration (FDA) investigated the blood clot concerns in April, it told states to pause use of Johnson & Johnson's shot. This, combined with the overall decline in vaccinations in the US and the public's hesitancy towards Johnson & Johnson's vaccine, has left states with millions of doses due to expire this month - and few people willing to take them.

Most Americans don't get to choose which vaccine they receive, but some pharmacies only offer certain brands, so people may choose their pharmacy accordingly.

CDC data shows that just 53 percent of Johnson & Johnson vaccines delivered to states have been administered, compared to 83 percent for Moderna and 84 percent for Pfizer. Just over 10 million Johnson & Johnson shots are still waiting to be given out, largely due to the decline in vaccination rates and the FDA-mandated pause.

Ohio Governor Mike DeWine said on Monday that the state had around 200,000 doses of the Johnson & Johnson vaccine set to expire on June 23, while Dr Jennifer Dillaha, Arkansas' state epidemiologist, said on June 2 that it was pausing new vaccine orders because it already had up to 60,000 doses of Johnson & Johnson's vaccine set to expire this month.

(With input from agencies)