CDC’s ACIP Votes to Recommend Pfizer’s Tick-Borne Encephalitis Vaccine

Tick-Borne Encephalitis (TBE) is a rare, but serious viral infection affecting the brain and spine. The virus is transmitted to people via either a bite from an infected tick, and, or by ingesting unpasteurized milk or milk products from infected animals. There is no cure or specific treatment for TBE, but its symptoms can be managed.

According to the Centers for Disease Control and Prevention (CDC), the risk of exposure for TBE is corresponding with the specific ixodid tick reservoir found in parts of Europe, the former Soviet Union, and Asia.

In an effort to prevent TBE, the CDCs Advisory Committee on Immunization Practices (ACIP) voted to recommend Pfizer’s TicoVac TBE vaccine yesterday. “Today’s ACIP recommendation is an important update that offers clear guidance to healthcare providers regarding when a TBE vaccine should be recommended to prevent infection,” Nanette Cocero, PhD, global president, Vaccines, Pfizer, said.

Pfizer’s TicoVac TBE vaccine induces protective antibodies against the 3 most prevalent subtypes of the TBEV circulating globally. According to the CDC, the TBE sub-types include: the European or Western tick-borne encephalitis virus; Siberian tick-borne encephalitis virus; and Far eastern Tick-borne encephalitis virus (formerly known as Russian Spring Summer encephalitis virus, RSSEV).

When Americans prepare to travel internationally, people may want to consider potential vaccines. “Those traveling to risk areas in Europe or Asia, whether for leisure or work, including military personnel, or those at risk of exposure to the TBE virus through laboratory work, are now able to have conversations with their health care providers about whether vaccination is the right option for them,” Cocero, said.

Trial Performance

In clinical trials, the safety and immunogenicity of TicoVac were assessed in 2 age cohorts (1-15 years of age and 16 years and above). Seropositivity rates were 99.5% in the former group and 98.7-100% in the latter group after 3 doses of the vaccine.

Pfizer reports the vaccine has acceptable safety and tolerability profile for both children and adults. Clinical studies demonstrated that the most common adverse reactions across both age groups were local tenderness, headache, local pain, fever, restlessness, fatigue, and muscle pain.

Next Steps

The vaccine was approved last August by the Food and Drug Administration, and Wednesday’s ACIP recommendation will be forwarded to the CDC director and the Department of Health and Human Services for review and approval. Once approved, the recommendations will be published in the Morbidity and Mortality Weekly Report (MMWR). The published recommendation will be accompanied by additional information around preventive measures to avoid tick bites.

TBE Incubation Period and Symptoms

“The incubation period of TBE is usually between 7 and 14 days and is asymptomatic. Shorter incubation times have been reported after milk-borne exposure. In contrast to Far-eastern TBE, European TBE is more severe in adults than in children where meningitis is more frequently observed.

In approximately two-thirds of patients infected with the European TBE virus, only an early (viremic) phase is experienced; symptoms are nonspecific and may include fever, malaise, anorexia, muscle aches, headache, nausea, and/or vomiting. After about 8 days of remission, a second phase of disease occurs in 20% to 30% of patients. These patients may experience a clinical illness that involves the central nervous system with symptoms of meningitis (e.g., fever, headache, and a stiff neck), encephalitis (e.g., drowsiness, confusion, sensory disturbances, and/or motor abnormalities such as paralysis), or meningoencephalitis, “as written on the CDC’s website.