Amid a shortage of monkeypox (MPOX) vaccine, the Food and Drug Administration (FDA) has announced a new strategy to help stretch the nation’s current supply by injecting only one-fifth of the vaccine’s usual dose. However, some worry that this strategy may leave people susceptible to the viral disease.
There are nearly 10,000 cases of monkeypox in the U.S. as of Wednesday, according to the Centers for Disease Control and Prevention (CDC). However, infectious disease experts think this number is likely an undercount, and national cases have been doubling about every 7.6 days, according to Trevor Bedford, a computational biologist at the Fred Hutchinson Cancer Center quoted in The Washington Post.
Approximately 1.5 million men who have sex with men (MSM) have been advised to get the vaccine since they are considered most at-risk for contracting MPOX. However, the U.S. only has 400,000 vials of vaccine currently in its Strategic National Stockpile, White House Monkeypox Response Coordinator Bob Fenton said Tuesday.
“In recent weeks the monkeypox virus has continued to spread at a rate that has made it clear our current vaccine supply will not meet the current demand,” said FDA Commissioner Robert M. Califf, M.D. in a statement. “The FDA quickly explored other scientifically appropriate options to facilitate access to the vaccine for all impacted individuals.”
To help stretch the currently available supply, the FDA has said that the vaccine can now be administered intradermally — that is, into the skin’s superficial layers — rather than through its usual subcutaneous method which injects the vaccine into the fat and connective tissues between the skin and muscular layers. The interdermal method could stretch the nation’s vaccine supply fivefold.
The possible effectiveness of the intradermal method is based on the results of a 2015 clinical study which showed that dendritic cells, part of the body’s immune system richly populated within the skin, are more efficient at generating an immune response than the cells in the subcutaneous layer. The method has been successfully used in prior mass vaccination campaigns against polio and rabies.
Future trials on this injection method could provide supporting data by the fall or winter, though it’s unclear if these trials will proceed, The New York Times reported.
The full MPOX vaccine requires two doses administered about a month apart. However, the vaccine shortage has compelled many local health providers to only administer a single dose.
A single dose is thought to give recipients about 85 percent immunity for two years, though the immunity only takes effect two to three weeks after the injection. A second dose offers increased immunity which lasts longer, but medical professionals think a single dose may sufficiently protect MSM against contracting MPOX, thus preventing a larger outbreak.
Regardless, some people worry that a single intradermal injection may not provide sufficient immunity, especially to those with compromised immune systems.
“We have grave concerns about the limited amount of research that has been done on this dose and administration method, and we fear it will give people a false sense of confidence that they are protected,” David Harvey, executive director of the National Coalition of STD Directors said in a statement. “This approach raises red flag after red flag, and appears to be rushed ahead without data on efficacy, safety, or alternative dosing strategies.”
Others worry that, because of the precision needed to administer an intradermal dose, an incorrect injection could leave people inadequately protected.
Part of the national vaccination shortage is due to the fact that most of the global supply of the Jynneos MPOX vaccine is produced by a tiny company in Denmark called Bavarian Nordic. Though the company can produce 30 million doses a year, its output and distribution have been hampered by the company’s lab renovation and supply chain disruptions.
While the U.S. has purchased most of the world’s available MPOX supply, most of it is currently stored in a frozen bulk substance that needs to be placed into stable vials before being shipped for use, Slate reported. In 2017, the U.S. also let nearly 28 million MPOX vaccines expire, not anticipating an eventual MPOX outbreak.
An additional 500,000 Jynneos doses are expected to reach the U.S. by the end of October.