Vaccines that Protect Against Infectious Respiratory Diseases

Most vaccine-preventable diseases are spread from person to person, which means that if one person in a community gets an infectious disease, they can spread it to others. The best way to help stop the spread of certain diseases is through vaccination. If enough people are vaccinated there are fewer chances for a vaccine-preventable disease to spread, keeping everyone healthier.

Understanding Respiratory Viruses

Infectious respiratory diseases such as influenza, COVID-19, and RSV spread from person to person. Learn how your body fights back against these pathogens and some of the common side effects that you may experience as your immune system attacks.

How Vaccines Work

A vaccine works by imitating an infection. It causes your immune system to start producing the same antibodies you would make if you were exposed to the real disease. This helps your body learn to recognize and fight an invasion of that virus or bacteria. Your body gets to develop immunity or learn how to defend itself from that disease without having to get infected from it first.

There are several kinds of vaccines. All vaccines have an active ingredient called an antigen that helps our body produce antibodies. These antigens can be either:

  • Weakened or killed bacteria or viruses
  • A piece of their exterior surface or genetic material, or
  • Bacterial toxin that has been treated so that it is now non-toxic

Vaccines Prevent Respiratory Diseases

What Respiratory Diseases Have Vaccines?

There are vaccines for some infectious respiratory diseases, including:

Some infectious respiratory diseases do not yet have a vaccine, including:

Talk to your healthcare provider to see if you are up to date on your vaccinations. Infectious respiratory disease can be unpredictable. It’s always better to prevent serious illness rather than treat it after it occurs.

Respiratory Immunization Coverage

Find out how you can get coverage of respiratory disease vaccines, including flu, COVID-19, and RSV with our Respiratory Immunization Coverage factsheet.
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Why Vaccinations are Important for Adults with Lung Disease

People with lung disease such as asthma or COPD may be at higher risk for serious illness from certain vaccine-preventable diseases. For best protection, it’s important to stay up to date on the following vaccinations:

  • COVID-19 – to protect against severe COVID-19 illness
  • Influenza – to protect against seasonal flu each year
  • Pneumococcal pneumonia – to protect against the most common type of bacterial pneumonia
  • RSV – to protect against severe RSV illness in adults ages 60 or older
  • Tdap – to protect against tetanus, diphtheria and pertussis (whooping cough)
  • Zoster – to protect against shingles

Vaccine-preventable diseases can cause long-term illness, existing chronic health conditions to worsen, hospitalization and death. Talk with your healthcare provider to be sure you are up to date with all recommended vaccinations for you.

A History of Vaccines

Vaccines have a long and impressive history. Well before we understood how infections worked, in the late 1700s an English physician Edward Jenner learned that giving small amounts of infected material from smallpox victims to others provided them protection from the dreaded disease. It was from those learnings that he developed a smallpox vaccine saving countless lives and small-pox has now been eradicated worldwide. Since that first vaccine was developed in 1798, we have used that same principle to produce vaccines to almost eliminate many of the formerly deadly childhood infectious diseases from the U.S.  In fact, the greatest vaccine success in the modern era has been the near worldwide elimination of polio.

But it’s not always that simple. Try as we might, we have not yet been able to develop successful vaccines to control other important worldwide infections, such as tuberculosis (TB), malaria and HIV. In addition, controlling influenza also remains a challenge requiring new vaccines each flu season.

How Vaccines Are Approved

Vaccine and new drug testing are overseen by the Food and Drug Administration (FDA) and are done in a similar way. Below is the typical process that FDA expects vaccine developers to follow to provide safety and effectiveness data of a vaccine.

The vaccine is extensively tested in cells or animals to see if it can elicit an immune response and identify any serious side effects. If animal testing seems safe and effective, this is when a group submits their study to the FDA for approval to move on to the next stage of testing.

This is the first time the vaccine is tested in small groups of healthy volunteers. Researchers will closely monitor for side effects and safety.

This stage is randomized, diverse, controlled and includes a larger number of participants. Individuals may include children, elderly, and other high-risk groups. The goal of this phase is to determine what variables may affect the safety of the vaccine, differences in immune responses, as well as the most effective dosage size and delivery method.

Researchers give the new medicine or treatment to an even larger group of participants to confirm its effectiveness, monitor side effects, and collect information that will allow the new medicine or treatment to be used safely. They measure effectiveness by comparing the people who get the vaccine to a control group of people who did not get the vaccine.

After a successful Phase III, the FDA will review the results and decide whether or not to approve it. The vaccine must be safe and effective, and the benefits of the vaccine must outweigh risks. If approved, the FDA will then license the vaccine for distribution. Once licensed, the FDA will continue to monitor the production, potency and effectiveness of the vaccine through.

If the need for the vaccine is urgent, such as with a public health emergency like the COVID-19 pandemic, the process for approving vaccines may be expedited. The FDA may issue an emergency use authorization (EUA) before all the testing is completed. But this will only happen if positive safety and effectiveness results are shown throughout all phases of testing. Adverse events are also noted and evaluated to see if they impact authorization. For an EUA to be issued for a vaccine, the FDA must determine that the known and potential benefits outweigh the known and potential risks of the vaccine.

Emergency Use Authorization for Vaccines Explained | FDA

Once vaccines are approved for use by the FDA, an advisory committee to the CDC made up of medical and public health experts called the Advisory Committee on Immunization Practices (ACIP will review all of the data. They then make a recommendation to add a vaccine to the vaccine schedule or not. The CDC Director then decides whether to approve the recommendation.

When vaccines are approved by FDA, they continue to be monitored for safety by several monitoring systems. CDC and ACIP can update their recommendation at any time as they continue to monitor vaccine-related risks and side effects.

Learn more by searching for recent vaccine topics covered in our Each Breath blog.

Ingredients in Vaccines to Protect Against Infectious Respiratory Diseases

Ingredients in vaccines generally fall into five categories, all of which have a specific purpose:

Antigens help our bodies build protection (immunity) to fight diseases

Stabilizers are used to protect the active ingredients in vaccines, so they are still able to do their job. Gelatin is a common stabilizer used in vaccines.

Adjuvants help boost the immune response after vaccination. This allows for lower doses of the vaccines and fewer doses. Vaccines containing adjuvants are tested extensively are evaluated by FDA scientists and physicians prior to approval. Adjuvants that are used in some vaccines that help prevent infectious respiratory diseases include:

  • Salts that contain aluminum which have been used in vaccines since the 1930s and we have over decades worth of data that help support that using aluminum salts in vaccines is safe. Aluminum salts can be found in diphtheria-tetanus-containing vaccines like DTaP and Tdap and pneumococcal vaccines. The exposure to aluminum from vaccines is minimal

The most common source of exposure to aluminum is from eating food and drinking water.

  • A saponin-based molecule (QS21 and Matrix-M) from the bark of Quillaja Saponaria trees. This is in the RSV vaccine indicated for adults, Arexvy and the Novavax COVID-19 vaccine.
  • A substance from the surface of bacteria that was modified for safety (Monophosphoryl lipid A). This is in the RSV vaccine indicated for adults, Arexvy.
  • Squalene oil emulsified (mixing substances that don’t typically mix, i.e. oil and water) in water to form MF59. This is in Fluad, a flu vaccine specifically for individuals 65+.

Remaining ingredients used to make the vaccine may be in the final vaccine product in small amounts including ingredients that are used to kill viruses or inactivate toxins (i.e. very small quantities of formaldehyde in diphtheria-tetanus-containing vaccines) or cell culture materials used to grow enough of the virus or vaccine to make the vaccine (i.e. egg protein used in the production of some, not all, flu vaccines).

Preservatives are used to prevent contamination in multi-dose vials. Bacteria could be introduced when putting a needle into the vial to draw up a dose of vaccine. Thimerosal, an ethylmercury-containing preservative has been scrutinized heavily and was removed from routine childhood vaccines as a precautionary measure in 2001. Most vaccines do not contain any mercury. Ethylmercury is often confused with methylmercury (found in fish), however they are very different. Ethylmercury is cleared from the body quickly and has not been shown in research to cause autism or neuropsychological delays.  Influenza vaccines are currently available in both thimerosal-containing (for multi-dose vaccine vials) and thimerosal-free versions, though there may be less or no thimerosal-containing flu vaccines in the upcoming season (2025-26) and beyond. Less than 5% of flu vaccines used in the United States contained thimerosal in past seasons.

Only necessary ingredients are added to vaccines used today. Vaccines go through extensive clinical trials and testing for safety before they are licensed. Once they become available, they are continuously monitored using several safety monitoring systems. For a complete list of vaccines, their ingredients and more information about each ingredient, please visit the Children’s Hospital of Philadelphia’s Vaccine Education Center.

Still Have Questions?

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Page last updated: July 15, 2025

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