Adenoviruses are a common group of viruses that can cause various illnesses in humans, from mild conditions like the common cold to more serious infections such as bronchitis, pneumonia, and gastroenteritis. While most adenovirus infections resolve without severe complications, outbreaks can occur, particularly in settings where people live in close quarters. A specific vaccine has been developed to prevent severe disease outbreaks in certain high-risk populations.
How the Adenovirus Vaccine Works
The adenovirus vaccine works differently from typical injectable vaccines. It is administered orally as two separate tablets, designed to be swallowed whole without chewing. One tablet contains live, but weakened, adenovirus type 4, while the other contains live adenovirus type 7. These two specific types are commonly associated with acute respiratory illnesses in congregate settings.
The tablets are specially coated to ensure they pass through the acidic environment of the stomach intact. Once in the intestines, the live, attenuated viruses are released and begin to replicate. This replication prompts the body’s immune system to develop protective antibodies against both adenovirus type 4 and type 7, establishing immunity without causing typical respiratory symptoms.
Target Population for Vaccination
The adenovirus vaccine is approved by the U.S. Food and Drug Administration (FDA) for use only in U.S. military personnel aged 17 through 50 years. It is routinely recommended for military recruits upon entering basic training. The Department of Defense uses it to prevent adenovirus-related respiratory disease in this population.
New recruits are particularly susceptible to adenovirus infections due to close-contact living and training environments in basic training. These confined settings facilitate rapid transmission, leading to potential outbreaks of acute respiratory disease. Historically, adenovirus infections caused significant illness among military recruits, often resulting in missed training. The vaccine mitigates these outbreaks and helps maintain troop health.
Safety and Side Effects
The adenovirus vaccine generally has a favorable safety profile, with most side effects being mild and temporary. Common reactions include gastrointestinal symptoms like abdominal pain, nausea, diarrhea, and vomiting. Some individuals may also experience upper respiratory symptoms such as headache, stuffy nose, sore throat, cough, and fever, or generalized body aches and joint pain.
More serious adverse events, such as pneumonia or inflammation of the stomach or intestines, have been reported rarely. It remains unclear if these problems are directly caused by the vaccine or occur coincidentally after vaccination. The vaccine has a long history of effectively preventing adenovirus outbreaks in the military, significantly reducing severe respiratory illness.
Adenovirus Vector Technology in Other Vaccines
Adenovirus vector technology is a distinct application of adenoviruses in vaccine development, different from the live adenovirus vaccine. In this approach, a common adenovirus is modified so it cannot replicate or cause disease. The modified adenovirus serves as a delivery vehicle, or “vector,” to transport genetic material from a different pathogen into cells.
For example, in the Johnson & Johnson COVID-19 vaccine, a modified adenovirus (specifically Ad26) carries the genetic instructions for the SARS-CoV-2 virus’s spike protein. Once the adenovirus vector enters a human cell, it delivers this genetic code. The cell then uses its own machinery to produce the spike protein, which is recognized as foreign by the immune system. This triggers an immune response, leading to the production of antibodies and T-cells that can protect against the target pathogen.
This vector-based method allows the body to develop immunity without exposure to the disease-causing virus. Beyond COVID-19, adenovirus vector technology has been explored in vaccines for other infectious diseases, including Ebola and influenza. This shows the versatility of adenoviruses as tools for delivering genetic information to stimulate a protective immune response.