(CNN)A hepatitis A outbreak has hit several states across the country, killing dozens of people and potentially sickening thousands. Michigan has been hardest-hit in terms of deaths, with 22.
The outbreak there began in August 2016 and, after a dropoff during the winter, continued to climb last year, according to the Michigan Department of Health and Human Services.
“We currently have 677 cases in Michigan and continue to see approximately 15-20 cases matching into the cluster every week,” Lynn Sutfin, spokeswoman for the Michigan Department of Health and Human Services, wrote in an email. “The Michigan outbreak now includes 15 different county jurisdictions. We believe that person-to-person transmission is the primary route of infection.”
Fighting the outbreak was challenging in some jurisdictions due to a national shortage of the vaccine for hepatitis A.
“Vaccine supply is still ‘constrained,’ ” Sutfin wrote. “We continue to prioritize vaccine to the highest risk individuals that have been identified and focus our vaccination efforts in the parts of the state who are experiencing the largest number of cases.”
Vaccine supplier Merck said the shortage of pre-filled syringes, the easiest to administer, would not ease until the second quarter of 2018. However, vials containing 10 single doses are available.
“The company is taking steps to continue to increase our capacity to meet demand globally in 2018,” Merck spokeswoman Pamela Eisele wrote in an email. “We apologize for any inconvenience this supply availability may be causing.”
The only other vaccine maker, GlaxoSmithKline, said it has adult hepatitis A vaccine in prefilled syringes in stock and is “working diligently to increase our supply.” The company is also working closely with the US Centers for Disease Control and Prevention, spokeswoman Robin Gaitens wrote in an email, to ensure that its vaccines “are directed to areas of greatest need.”