As of Thursday, San Francisco clinics are starting to administer monkeypox vaccines using a new split-dose technique intended to stretch the limited supply. Using a new injection method, each single-dose vial of the Jynneos vaccine can be used to immunize five people. Some experts applauded the new strategy, but others have expressed concerns.
"I fully endorse the idea of trying to get five doses out of one vial," Dr. Monica Gandhi, medical director of the Ward 86 HIV clinic at Zuckerberg San Francisco General Hospital and Trauma Center told the Bay Area Reporter. "In this time of scarcity, we need higher rates of immunity across a larger swath of gay men. I endorse this as a temporary strategy until we can get more vaccines."
As of August 18, the Centers for Disease Control and Prevention has identified 14,115 monkeypox cases in the United States. Worldwide, there are now more than 40,000 cases. With race and ethnicity data now available for more than 6,000 U.S. cases, 35% are white, 33% are Latino and nearly 28% are Black, CDC director Dr. Rochelle Walensky said during an August 18 media briefing. This shows a further shift toward people of color since the CDC's last demographic report.
San Francisco cases stand at 618, according to the health department.
While anyone can get monkeypox through close physical contact, cases remain heavily concentrated among gay, bisexual, transgender and other men who have sex with men. So far, 98% of cases with available data were among men, and 93% reported recent sexual contact with other men, according to Walensky. Experts estimate that some 1.5 to 2 million men who have sex with men are at substantial risk for monkeypox, but most do not expect the virus to spread widely outside this group.
Other federal officials participating in the briefing gave an update on the administration's monkeypox response strategy. Dawn O'Connell, the Department of Health and Human Services assistant secretary for preparedness and response, said the government has delivered more than 1 million doses of the Jynneos vaccine, with another 1.8 million more doses on the way. In addition to their regular allocations, jurisdictions will now be able to request additional doses to administer at large LGBTQ events such as the upcoming Southern Decadence weekend in New Orleans.
But the new vaccine numbers can be misleading. As of this week, the government will report vaccine distribution assuming providers are using the new fractional-dose administration method, so while it may look like the supply has increased dramatically, this reflects the fact that what was formerly one dose is now considered five doses.
Vaccine effectiveness
Monkeypox is related to smallpox, but less severe, and smallpox vaccines can prevent monkeypox too. Jynneos, a safe nonreplicating alternative to older smallpox vaccines, was approved in 2019. Its original indication calls for two doses administered as traditional subcutaneous injections four weeks apart. But on August 9, the federal Food and Drug Administration issued an emergency use authorization that allows it to be administered by intradermal injection, splitting a single vial into five doses. Recipients should still get two doses about a month apart.
The monkeypox vaccine supply has been severely limited, leading to long queues and growing frustration in San Francisco and other hard-hit cities. In an effort to overcome the shortage, many cities have resorted to a one-dose strategy to give twice as many people partial protection as soon as possible, rather than holding second doses in reserve. The new intradermal administration method will stretch supplies even further.
The skin contains plentiful immune cells, known as dendritic cells, that recognize viral antigens in the vaccine and trigger a strong immune response. The intradermal injection method is already used for other diseases, but it requires special training to administer the shot at an angle under the upper layer of skin, and it can cause worse injection site reactions such as redness and itching.
Little is known about the real-world effectiveness of the Jynneos vaccine, as most data comes from animal research and studies of antibody responses in humans. One study found that antibody levels were similar after traditional subcutaneous and intradermal vaccine administration, but it's important to get both doses.
Walensky said that while the government expects the new vaccination method to offer protection, much remains to be learned.
"To be clear, we're learning how well the vaccines work against monkeypox and in this specific outbreak," she said. "Although we anticipate vaccines will provide protection, temporarily reducing or avoiding behaviors that increase your risk of monkeypox exposure is important, especially in between your first and second doses of the vaccine. From what we know right now, we expect protection to be the highest two weeks after the second dose of the vaccine."
Jynneos manufacturer Bavarian Nordic recently sent a letter to HHS expressing reservations about the intradermal approach given the "very limited safety data" and the fact that many clinical trial participants never received their second dose, the Washington Post reported.
Some people in this outbreak have reportedly gotten monkeypox despite vaccination, especially if they were exposed soon after their first shot. "Vaccines are not a silver bullet," World Health Organization monkeypox technical lead Dr. Rosamund Lewis said during an August 17 briefing. "We're not expecting 100% efficacy of these vaccines for the prevention of monkeypox."
Some experts caution that the one-dose strategy and intradermal administration may not be appropriate for people with HIV, who may have weaker immune responses even if they're on effective antiretroviral treatment. This suggests HIV-positive people should be prioritized to receive the optimal number of doses using the most effective administration method. Up to half of people with monkeypox are living with HIV, according to U.S. and European case reports.
"I think those with low CD4 counts should not get this intradermal dose. I would use 350 as a cut-off," Gandhi said.
The intradermal injection technique also should not be used when a person has keloids, an overgrowth of scar tissue that is more common among Black people, according to the DPH.
SF DPH adopts new method
SF DPH has instructed vaccine providers to begin using the intradermal method as soon as August 18 and expects that most sites will completely switch over by the time the next vaccine allocation arrives, according to a statement sent to the B.A.R. The intradermal method requires updated protocols and additional training for many vaccine providers, and it may be slower to administer, but it allows DPH to move up the timeline on expanding vaccine eligibility and administering second doses.
Despite the ongoing shortage, the monkeypox vaccine clinic at SFGH has been able to serve all walk-in clients in recent days. However, the San Francisco AIDS Foundation's Magnet sexual health clinic in the Castro still has a "sizeable waiting list" of nearly 12,000 people, according to SFAF spokesperson Emily Land.
"We are not using the intradermal dosing strategy yet," SFAF CEO Dr. Tyler TerMeer, Ph.D. told the B.A.R. "We are supportive of measures that extend the reach of the Jynneos vaccine, although there are things that still need to be worked out in terms of provider training and the ability of health care providers across the board to implement this new dosing."
Those currently eligible for vaccination in SF include people who have had close contact with a person with monkeypox, those who have attended venues or events where a case was identified, gay and bisexual men and trans people who have had more than one sex partner in the past two weeks, sex workers of any sexual orientation or gender identity, and certain clinicians and laboratory workers. Ideally, DPH aims to expand eligibility to include people who are at risk even if they have not recently had multiple sex partners, for example those who are taking PrEP for HIV prevention.
"A single-dose vial can be split when the intradermal method is used, extending the number of San Franciscans we can vaccinate by as many as fivefold," DPH stated. "Switching to a new technique of administering doses takes time, but by leveraging city partners and collaborations with community organizations, we are creating a wider network of vaccine providers to create more access to the vaccine and support our most impacted communities, just as we did with COVID-19."
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