As monkeypox cases in the US climb and the preferred vaccine remains in short supply, the Centers for Disease Control and Prevention (CDC) is pushing back against calls to provide people with a single shot of the vaccine, rather than the recommended two doses.
This strategy would extend the supply of the highly in demand JYNNEOS vaccine and hypothetically curb spread by giving a greater number of people immunity against the virus in less time. This may seem logical, especially inasmuch as cases are expected to continue rising in the coming weeks; however, a single dose does not provide enough protection against the virus, officials said during a July 15 press call, and thus the strategy could risk further infections and spread of the virus.
“Like many vaccines, it takes time for your body to build antibody protection against vaccination,” said CDC Director Rochelle Walensky, MD, MPH, during the call. “The clinical trials and immunologic studies of the JYNNEOS vaccine show that a single dose of vaccine does not produce the levels of antibody that we would expect are needed for full protection from monkeypox, especially in the context of potential for repeated high-risk exposure.”
The JYNNEOS vaccine is administered in two doses that are delivered 28 days apart. People typically have maximum immunity against monkeypox 2 weeks after receiving the second dose.
As of July 14, 1470 cases of monkeypox had been reported in the United States. Of 700 cases for which demographic information was available, the median age of the patients was 36. The “vast majority” of cases have been in men who have sex with men, Walensky said. She said she was aware of eight individuals who were diagnosed with monkeypox and who were assigned female sex at birth, but she also noted that there are gaps in data with respect to information about gender.
While monkeypox is now a reportable disease in the US, demographic information on these cases is voluntarily shared with the CDC, she added.
Walensky said that cases are expected to continue increasing in the following weeks because of a transition to a more streamlined monkeypox case reporting system, infections from resulting monkeypox exposures, and an increasing number of people seeking monkeypox tests. Since July 6, monkeypox tests conducted at state public health labs had risen 76%.
But officials are confident that US testing capacity will meet the increasing need. Now, the US can test 70,000 samples per week, Walensky said. She noted that so far, testing capacity has far surpassed the demand. “Now, we must look to our clinicians and public health colleagues to ensure proper patient education, proper screening and counseling is taking place so that patients are tested, cases are identified, and proper treatment and prevention are taking place,” she noted.
During the press call, federal officials announced that an additional 130,000 doses of JYNNEOS had arrived at the strategic national stockpile. These will be delivered to states as early as Monday, July 18. States can also request the ACAM 2000 vaccine, which is approved for protection against smallpox but can also protect against monkeypox.
But this vaccine has more side effects and cannot be given to people with heart disease or those who are immunocompromised. A few states have requested ACAM2000 in “relatively modest quantities,” said Dawn O’Connell, JD, assistant secretary for preparedness and response at the Department for Health and Human Services in the press call.
Officials also announced that they have ordered an additional 2.5 million doses of JYNNEOS, which will arrive next year. By mid-2023, the federal government will have received seven million doses of the vaccine.
Currently, demand for the vaccine exceeds the states’ supply, Walensky said, adding, “we know that this is frustrating.”