**10. Adenovirus vaccines**

Adenovirus infection is perhaps the only respiratory disease other than influenza, against which specific prevention methods have been developed. Military contingents in the United States since 1971 are vaccinated with live oral adenovirus vaccine against serotypes 7 and 4 which were isolated in the 1950s [27]. Live oral adenovirus vaccine has proven to be safe and highly effective in numerous clinical trials, as well as in clinical observations of acute respiratory infections among US military personnel. However, live oral adenoviral vaccine types 4 and 7 are approved only for use in military teams for adults 17–50 years old. To avoid the virus being thrown into the upper respiratory tract, it is recommended to swallow the tablets whole, without chewing. Adenovirus is extremely stable under natural conditions, and there is the possibility of being released into the environment through excreta. Therefore, a vaccine containing live strains of adenovirus is not recommended for use in children or the general population. Despite the longterm stability of the adenovirus genome, which is confirmed by the efficacy of ongoing vaccination among the US military, random mutations or homologous recombination events, which can lead to changes in the antigenicity of adenovirus, are not excluded. In addition, over time, the epidemic types of adenovirus have changed, and in recent years, highly pathogenic serotypes 14 and 55 have been distributed throughout the world. Finally, the circulation of the types of adenoviruses can vary geographically; for example, in China, the most common types associated with acute respiratory infections (ARI) are types 3, 7, and 55 [28]. Therefore, attention should be paid to developing new adenoviral vaccines based on currently circulating adenovirus strains.
