Respiratory infections are caused by numerous viruses, bacteria and, less commonly, other microorganisms, so prevention requires multiple layers of protection rather than one universal measure. Core strategies include staying up to date with recommended vaccinations, practising hand and respiratory hygiene, improving indoor air quality, avoiding close contact with people who are acutely infectious and staying home when ill. The specific importance of each intervention varies according to the organism and route of transmission. Influenza, COVID-19 and respiratory syncytial virus, for example, can spread through respiratory particles, while some respiratory infections have additional transmission routes. Effective prevention therefore begins with understanding how the relevant pathogen moves between people and then interrupting that pathway.
Vaccination is one of the most important specific preventive interventions for respiratory infections for which effective vaccines exist. Vaccines expose the immune system to an antigen or antigenic information in a controlled manner so that immune memory can develop without requiring the person to experience the disease itself. Subsequent exposure can then produce a faster and more effective immune response.
Vaccination does not necessarily prevent every infection, because immunity can decline, pathogens can evolve and vaccines vary in effectiveness, but it can substantially reduce severe disease and other important outcomes. Influenza and COVID-19 are prominent examples where vaccination is used as part of respiratory-disease prevention. Vaccine recommendations vary according to age, health status, pregnancy, season, country and circulating pathogens.
Cleaner indoor air is particularly important for infections that can spread through respiratory particles. Ventilation replaces indoor air containing exhaled particles with cleaner air, while filtration can remove particles from recirculated air. Portable air cleaners equipped with appropriate filters can provide additional removal of airborne particles in some environments. Outdoor settings generally provide greater dilution of respiratory emissions than enclosed spaces, although outdoor transmission can still occur under particular conditions. Building design, airflow direction, occupancy, room volume and duration of exposure all influence effectiveness. Cleaner air is therefore an environmental control that complements rather than replaces vaccination, staying home when sick, masking and other measures.
Hand and respiratory hygiene reduce transmission opportunities. Washing hands with soap removes microorganisms and contaminated material, while alcohol-based hand sanitiser containing at least 60 percent alcohol can be used when soap and water are unavailable. Covering coughs and sneezes with a tissue or the elbow reduces dispersal of respiratory secretions, and frequently touched surfaces can be cleaned with appropriate household products. Hand hygiene is particularly relevant because microorganisms on the hands can subsequently reach the nose, mouth or eyes. The relative importance of surface transmission differs between pathogens, but hygiene remains a practical and low-cost prevention measure that can reduce exposure to a broad range of infectious organisms.
Staying away from others when infectious is another major prevention strategy. People with respiratory symptoms can spread pathogens even when symptoms are relatively mild, and some infections can be transmitted before symptoms are recognised. Current CDC guidance recommends staying home and away from others while respiratory symptoms are not improving and returning to normal activities once symptoms are improving overall and fever has been absent for at least 24 hours without fever-reducing medication. Additional precautions for five days after returning to normal activities can further reduce transmission. This approach is particularly important around people who have an increased risk of severe respiratory disease.
Masks and physical distancing can add further protection when respiratory viruses are circulating or when someone is recovering from an infection. A well-fitting mask can reduce the amount of infectious material a person inhales and, depending on the mask and circumstances, can also reduce the amount released by an infected wearer. Physical distancing reduces exposure by increasing the separation between a potentially infectious source and a susceptible person. These measures become particularly useful in crowded indoor environments, around people at increased risk of severe illness, after recent exposure or when someone must interact with others while recovering. They are additional layers rather than substitutes for vaccination and cleaner air.
Prevention also depends on recognising individual vulnerability and the infectious context. Older adults, infants, people with certain chronic diseases and people with weakened immune systems can face higher risks from respiratory infections. Additional precautions can therefore be justified when vulnerable people are present, even if the illness would normally be mild for a healthy adult. Testing can sometimes identify a specific infection and guide decisions about treatment or precautions. Prompt medical assessment is particularly relevant for people at high risk because early treatment for infections such as influenza and COVID-19 can reduce the risk of severe outcomes when appropriate therapies are started promptly.
No prevention measure provides absolute protection, because pathogens differ, exposures are difficult to predict and human behaviour cannot eliminate all transmission. Effective infection prevention instead uses the concept of layered controls: vaccination reduces susceptibility and severity, cleaner air reduces airborne exposure, masks reduce inhaled or exhaled particles, distancing reduces close exposure, hygiene interrupts some contact routes, and staying home while infectious removes opportunities for transmission. This layered approach is more robust than relying on a single intervention. It also explains why prevention recommendations can change according to the pathogen, season, community transmission level, setting, individual vulnerability and availability of effective vaccines or treatments.
