LOS ANGELES (CNS) — Los Angeles County opened an additional monkeypox vaccination site Thursday — one day after officials announced the county this week had received less than half the number of new doses it originally anticipated.

Despite the unexpected shortfall, however, health officials said the county will still begin offering second doses of the two-shot regimen to those eligible for it. The county also announced Thursday an expansion of vaccine eligibility to include those under age 18 who are considered at high risk of infection.

County Health Officer Dr. Muntu Davis also said Thursday the county had confirmed its first known monkeypox case at a jail, and the first at a homeless shelter. Details of those patients were not released, but Davis said the county was performing contact tracing and vaccinating people who were exposed.

Meanwhile, Supervisor Hilda Solis announced the opening of the new vaccination site at the Jack Crippen Senior Center at 3120 Tyler Ave. in El Monte.

Depending on the availability of limited vaccine supply, some 100 residents can be vaccinated on Tuesdays, Thursdays and Fridays from 10 a.m. to 3 p.m. at the new site, Solis' office said.

Residents must be pre-registered and have received a verification text to be vaccinated.

Solis also cautioned that, as with all monkeypox vaccination sites, operations may be paused depending on available vaccine supply.

"While we work with the federal government to increase the supply of the monkeypox vaccine for Los Angeles County residents, setting up pop-up vaccination clinics in communities such as El Monte is critical to ensuring our available vaccines are distributed equitably," Solis said.

"With the launch of the monkeypox vaccination site at Jack Crippen Senior Center, the county is building a vaccination network that will be accessible to residents of color to provide as many doses as possible."

According to the county Department of Public Health, the county this week had anticipated receiving 14,000 vials of vaccine — enough to administer 70,000 shots — but got word from the federal government that it would actually be receiving only 5,600 vials, enough to administer 28,000 doses.

"Public Health has received assurances from the federal leadership that additional doses will be available in the coming weeks," according to a statement from the agency.

Rep. Adam Schiff, D-Burbank, announced Wednesday that he and 10 other members of the Southern California Congressional delegation have sent a letter to U.S. Health and Human Services Secretary Xavier Becerra stressing the "urgent" need to address the area's shortfall.

"We are encouraged by the Biden administration's recent actions declaring monkeypox a public health emergency and issuing an emergency use authorization to help expand JYNNEOS vaccine supply," the legislators wrote.

"While these are critical steps in the public health response to MPV, we strongly urge the Department of Health and Human Services, in coordination with the White House, to take further steps to procure and distribute additional JYNNEOS vaccine doses to ensure areas that have been hardest hit, including Los Angeles, have adequate vaccine supply."

Despite the smaller-than-anticipated allocation, the county will still begin offering second doses of the vaccine to roughly 8,000 people eligible to receive them. The second doses will be available to people who received their first dose at least 28 days ago, with the shots available either through a personal health care provider or through the county's registration system, if they received the initial dose from the county.

Another 19,000 doses from the weekly allocation will be distributed to community providers and public vaccination sites to be used as first doses. In addition, 1,000 doses will be reserved for close contacts of existing patients, for outbreak control and special populations at high risk of infection.

The county this week transitioned to a newly approved method of administering smaller doses of the monkeypox vaccine, a move that led to a five- fold increase in the availability of shots locally.

The U.S. Food and Drug Administration last week allowed the JYNNEOS vaccine to be administered between layers of skin, in what's called an intradermal injection. Previously, the vaccine was administered beneath the skin, in a subcutaneous injection. The intradermal method requires only roughly one-fifth the amount of vaccine required by the subcutaneous injection, authorities said.

Making the change is designed to stretch the limited of supply of the vaccine nationally, allowing smaller doses to be administered to more people.

The county has simplified its previously complex system for determining who is eligible to receive a monkeypox vaccine. The shots are now available to any gay or bisexual man or transgender person age 18 and older who has had multiple or anonymous sex partners in the previous 14 days.

Davis said Thursday the county was also expanding eligibility to those under age 18 "who are determined to be a high risk of monkeypox infection."

All minors must have consent from a parent or guardian to be vaccinated. Those aged 16 or 17 should be accompanied at a vaccination site by a parent or guardian, if possible, or they can simply present a signed consent form. Those under age 16 must have a parent or guardian present to get vaccinated, in addition to a signed consent form, Davis said.

Minors under age 18 are not eligible for the intradermal injection, so they must receive the full subcutaneous dosage, under the terms of the emergency use authorization for the shots approved by the U.S. Food and Drug Administration.

People who were eligible under the county's previous guidelines will remain eligible for the shots.

The previous guidelines made shots available to people confirmed by the Department of Public Health to have had high- or immediate-risk contact with a known monkeypox patient, and to people who attended an event or visited a venue where there was a high risk of exposure to a confirmed case.

Shots were also available for gay and bisexual men and transgender people with a diagnosis of rectal gonorrhea or early syphilis within the past year. Also eligible for the shots are gay or bisexual men or transgender people who are on HIV pre-exposure prophylaxix, or PrEP, or who attended or worked at a commercial sex venue or other venue where they had anonymous sex or sex with multiple partners — such as at a sauna, bathhouse or sex club — in the past 21 days.

Residents who fall into the eligibility criteria can register online at ph.lacounty.gov/monkeypoxsignup to be alerted when a vaccine dose is available.

As of Thursday, the county has identified 1,036 confirmed or probable cases of monkeypox — including those in Long Beach and Pasadena, which both have their own health departments — up from 738 last Thursday. Almost all of the cases are in men, the majority of them gay or bisexual.

Monkeypox is generally spread through intimate skin-to-skin contact, resulting from infectious rashes and scabs, though respiratory secretions and bodily fluids exchanged during extended physical episodes, such as sexual intercourse, can also lead to transmission, according to the U.S. Centers for Disease Control. It can also be transmitted through the sharing of items such as bedding and towels.

Symptoms include fresh pimples, blisters, rashes, fever and fatigue. There is no specific treatment. People who have been infected with smallpox, or have been vaccinated for it, may have immunity to monkeypox.

According to health officials, the vaccine can prevent infection if given before or shortly after exposure to the virus.

More information is available online.