Published on Infectious Disease Special Edition on August 18, 2021
The FDA approved a tickborne encephalitis (TBE) vaccine (TicoVac, Pfizer) for active immunization to prevent this viral disease in people 12 months of age and older.
This is the only vaccine with an indication to help protect U.S. adults and children against the flavivirus when visiting or living in TBE endemic areas. The CDC’s Advisory Committee on Immunization Practices (ACIP) is expected to discuss recommendations on the safe and appropriate use of the vaccine.
A viral infection of the brain and spine, TBE can be transmitted to humans through the bite of an infected Ixodes tick. It can also be transmitted by ingestion of unpasteurized milk or milk products from infected animals, but this occurs less frequently. The disease may initially be mistaken for summer flu, but can be a serious condition with possible long-term consequences. One in three people can have long-term effects that last months or years, including cognitive changes, muscle weakness or permanent paralysis, and in rare cases (0.5%-2%; up to 20% in Russia), people may die. TBE can affect people of any age who come in contact with ticks whenever they do outdoor activities in countries where ticks infected with TBE are prevalent.
Although TBE is not endemic in the United States at this time, it has been identified in more than 35 countries across Europe and Asia. The European Centre for Disease Prevention and Control currently recommends TBE vaccination for people who live in or are traveling to risk areas.
The vaccine has been used for more than 45 years outside the United States, and more than 170 million doses of the vaccine have been distributed since 1976.
Pfizer’s TBE vaccine is developed using a master seed virus that is similar to the TBE virus found in nature. It is able to induce neutralizing antibodies against the natural TBE virus, as the sequence and structure of the virus subtype match those found in nature (Vaccine 2011;29:7307-7319).
In clinical trials, the safety and immunogenicity of the TBE vaccine was assessed in two age groups: 24 months to 15 years, and older than 16 years. In these studies, seropositivity rates were 99.5% in the younger group and 98.75% to 100% in the older group following three doses (J Infect Dis 2011;203:1556-1564). Clinical studies demonstrated that the TBE vaccine was generally well tolerated, with no unexpected adverse events or vaccine-related serious adverse events observed (Vaccine 2007;25[43]:7559-7567).
The most common adverse reactions in both age groups were local tenderness, headache, local pain, fever, restlessness, fatigue and muscle pain. Real-world studies from Austria have shown that the vaccine is 96% to 98.7% effective in people who have received at least three doses of the vaccine.
“We are proud to deliver the first vaccine to help protect people in the U.S. against TBE, if they are traveling to any risk areas,” said Nanette Cocero, PhD, the global president of vaccines at Pfizer. “This vaccine has helped to protect millions of people in TBE endemic regions since its first approval outside the U.S., 45 years ago. This authorization helps to ensure that people from the U.S. are also able to receive this vaccination if needed, reflecting our commitment to provide health for all.”