Monkeypox Vaccines: California and FDA Do Not Agree on How to Stretch Meager Supply

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A person in an orange baseball cap and blue surgical mask presses a needle into the arm of an person who is sitting outside.
A public health worker administers the monkeypox vaccine at the Balboa Sports Center in the Encino neighborhood of Los Angeles, California, on July 27, 2022.  (Photo by ROBYN BECK/AFP via Getty Images)

As monkeypox spreads rapidly, everyone agrees that the meager supply of vaccine needs to be improved.

But how exactly to stretch the limited supply? That’s where California and its progressive cities have diverged from federal regulators.

California’s top health officials advised local agencies in a July 27 memo to prioritize a single dose of the two-dose monkeypox vaccine for people who are most at risk. For weeks, San Francisco has used this strategy to spread its limited supply of monkeypox vaccine to people in the city who are at high risk of contracting the disease.

Officials with the Centers for Disease Control and Prevention and the Food and Drug Administration have warned health providers against deviating from the approved schedule. The vaccine is supposed to be given in two doses, with the second one administered 28 days after the first.

“We do not recommend to go off of the recommended schedule here,” said Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, at a press conference organized by the Department of Health and Human Services. For people most at risk, he added, “A single dose of this vaccine will not provide the kind of protection over time that is necessary."

'Dose sparing'

Now, the FDA is considering a "dose sparing" proposal that would allow health providers to use a single-dose vial of vaccine to administer a total of up to five separate doses. The plan would require changing how the vaccine is administered. Rather than an injection that goes into the fatty tissues underneath the skin, known as subcutaneous administration, people would receive it through a small needle placed delicately under the top layer of skin.

This is called intradermal administration, and giving vaccines intradermally can also result in a strong immune response.

"The FDA has identified a potential solution that would allow us to significantly increase the number of doses available [for] administration," an agency spokesperson told KQED in an emailed statement on Friday.

"It’s important to note that overall safety and efficacy profile would not be sacrificed with this approach,” the statement said. “The virus has continued to spread at a pace and rate in recent weeks that made it clear to all of us that we would not meet current demand with the current supply."

The FDA’s alternate strategy is now under consideration and not yet approved — nor is it clear when it might be.

The single dose strategy

Health experts warn that the U.S. might not be able to contain the monkeypox outbreak, which has already infected thousands of Americans. And San Francisco has said it is important to take quick action in order to protect the most people.

KQED’s Community Engagement Reporter Carlos Cabrera-Lomelí reported that people seeking a jab at a vaccine clinic at Zuckerberg San Francisco General Hospital and Trauma Center are not being offered second shots right now.

Instead, San Francisco’s health department is prioritizing first doses of Jynneos, delaying the second. Cabrera-Lomelí reported that patients attending the clinic at Zuckerberg San Francisco General Hospital and Trauma Center, the city’s only walk-in monkeypox vaccine clinic, were told by hospital staff that their second shot could safely be delayed as long as two years.

City officials told KQED in an email that "although data on the full efficacy of a first dose of the Jynneos monkeypox vaccine is not fully known, the information that we do have and relevant studies on the topic, allows us to take this temporary harm reduction approach while vaccine supply increases."

California’s health department laid out a rationale for a single shot plan in the memo it sent to local agencies, noting that in the eradication of smallpox — a poxvirus genetically very similar to monkeypox — the first vaccine dose provided quick protection. Clinical trials in humans and animals measuring immunity from the Jynneos have produced similar results.

"While supplies remain scarce, vaccinators in California may offer first doses of JYNNEOS [sic] to additional persons at risk rather than retain inventory as second doses for immunocompetent persons, even if second doses are consequently administered at an interval greater than 28 days," the memo said.

The health department said people who are immunocompromised are still eligible to received two doses. 

UCSF’s Dr. Peter Chin-Hong told KQED in an email that it "is indeed safe not to get a second dose of the vaccine at 28 days, on time."

New York, the United Kingdom and Canada are delaying the vaccine boosters, too. Science magazine reported that  Paul Chaplin, an immunologist and CEO of Bavarian Nordic — the company that manufactures the vaccine — also endorses the single dose plan.

Federal scientists have cautioned that a single dose regime of vaccine hasn’t been studied in an actual outbreak.

Jynneos is the only vaccine currently approved for the prevention of monkeypox in the United States.

San Francisco health officials say people, "especially those who have only received one dose," should limit their risk of exposure to monkeypox before and after being vaccinated and second doses will be offered "once supply allows."