(The Hill) – The White House on Tuesday said it plans to send out tens of thousands of vaccine doses immediately as the nation tries to head off a growing monkeypox outbreak, amid fears that the country is undercounting cases because of insufficient testing.  

Administration officials ​said the vaccine strategy will focus on protecting those most at-risk of monkeypox, and will use a tiered distribution system to prioritize vaccines for areas with the highest numbers of cases.

The Centers for Disease Control and Prevention (CDC) has confirmed about 300 cases of monkeypox in the U.S., though the actual number could be higher.  

The administration plans to allocate 296,000 doses of the Jynneos vaccine over the coming weeks, which is the only Food and Drug Administration-approved vaccine specifically for monkeypox.

Of those, 56,000 doses that are in the Strategic National Stockpile will be allocated immediately. Over the coming months a combined 1.6 million additional doses will become available, the White House said.

The CDC is recommending that the new vaccine doses be provided to individuals with confirmed monkeypox exposures and presumed exposures, rather than only those who have a confirmed case.

This includes those who had close physical contact with someone diagnosed with monkeypox, those who know their sexual partner was diagnosed with monkeypox, and men who have sex with men who have recently had multiple sex partners in a venue where there was confirmed monkeypox, or in an area where monkeypox is spreading.

Health officials said close contact, and sexual contact in particular, appear to be the primary drivers for this outbreak. 

“As case counts and the number of jurisdictions with cases increases, the need for medical countermeasures, including vaccines, continues to rise,” CDC Director Rochelle Walensky told reporters during a media briefing Tuesday.

“The administration’s current strategy is focused on containing the outbreak by providing vaccines to those most in need to prevent further spread of monkeypox in the communities most impacted, and as additional supply becomes available, we will further expand our efforts making vaccines available to a wider population,” Walensky said. 

The virus has been disproportionately spread among gay and bisexual men, though health authorities and LGBTQ advocacy groups have repeatedly stressed that monkeypox does not differentiate between those who are gay or straight and that everyone should stay aware and informed on the risks of the virus.

When monkeypox cases began cropping up around the U.S., federal health authorities said there were about 72,000 doses of Jynneos in the Strategic National Stockpile, a paltry amount compared to the more than 100 million doses of ACAM2000, an older smallpox vaccine.

Local and state governments have so far expressed a preference for the newer Jynneos smallpox vaccine due to concerns over the possible side effects associated with ACAM2000. 

According to the White House, the Jynneos vaccine will be allocated using a four-tier distribution strategy that prioritizes jurisdictions with the highest case rates of monkeypox.

Within each tier, doses of Jynneos will be allocated based on the number of individuals at risk for monkeypox who also have a contraindication to ACAM2000, such as those with HIV.