Inactivated vaccine

An inactivated vaccine (or killed vaccine) is a special kind of vaccine that helps protect people from diseases. It uses germs like viruses or bacteria that have been killed so they can't make you sick. Unlike live vaccines, which use weakened but still living germs, inactivated vaccines use germs that are completely unable to grow or cause illness.

These vaccines were first made in the late 1800s and early 1900s to fight diseases such as cholera, plague, and typhoid. A big breakthrough came in the 1950s when Jonas Salk created an inactivated vaccine for the polio virus, which helped stop the spread of this serious disease. Today, inactivated vaccines are used for many illnesses, including influenza, polio, rabies, hepatitis A, CoronaVac, Covaxin, and pertussis.

Because the germs in inactivated vaccines are dead, they sometimes need extra help to make the body's immune system react strongly enough. This is why some inactivated vaccines include special ingredients called immunologic adjuvants or need extra shots called "booster" doses. While live vaccines often work well for healthy people with just one dose, inactivated vaccines are important for those who can't safely take live vaccines, such as elderly people or individuals with immunodeficiency.

Mechanism

When we get an inactivated vaccine, the germs in it have been killed so they can’t make us sick. But they still look enough like real germs for our body to recognize them and prepare to fight them off. This helps our immune system remember how to protect us if we ever meet the real germs.

Inside our body, special cells pick up a piece of the vaccine and show it to other cells. This helps our body make antibodies and remember the germ, so it can respond faster if we are exposed to it later. These vaccines mainly help our body make antibodies, but with the right ingredients, they can also help in other ways.

Social Consequences

Inactivated vaccines have played a big role in keeping people healthier and safer. By helping stop diseases like tetanus, diphtheria, and pertussis, these vaccines made communities stronger and healthier. In places where many people get vaccinated, it helps protect everyone, even those who can’t get vaccines themselves.

Vaccines for diseases such as polio, hepatitis A, and influenza mean fewer people get very sick. This lets families focus on everyday life instead of caring for sick loved ones, and children can go to school without worrying about getting sick. Because of this, people trust health services more, and getting vaccines like the yearly flu shot or childhood immunization becomes a normal, regular part of staying healthy.

Types

Inactivated vaccines are made by different methods to stop the germ from making people sick.

Some vaccines use the whole germ that has been killed by heat, chemicals, or radiation. Two common chemicals used are formaldehyde and beta-Propiolactone.

Other vaccines use just parts of the germ, made by breaking open the virus with a special liquid. This method is often used for flu vaccines.

Sometimes, the word "inactivated vaccines" is used to mean any vaccine that is not made with live germs, which can also include subunit vaccines and toxoid vaccines.

Examples

Inactivated vaccines help protect people from many diseases. Some common viral examples include the injected polio vaccine (also called the Salk vaccine), hepatitis A vaccine, rabies vaccine, most influenza vaccines, tick-borne encephalitis vaccine, and some COVID-19 vaccines like CoronaVac, Covaxin, QazVac, Sinopharm BIBP, Sinopharm WIBP, TURKOVAC, and CoviVac.

Bacterial examples include the injected typhoid vaccine, cholera vaccine, plague vaccine, and whole-cell pertussis vaccine.

Advantages and disadvantages

Inactivated vaccines have some benefits and drawbacks. One advantage is that the pathogens in these vaccines are more stable, making them easier to store and transport. They also cannot become harmful and cause illness, unlike some live vaccines. This makes them safe for people whose immune systems are weak.

However, inactivated vaccines may not create as strong or long-lasting protection as live vaccines. They often need extra ingredients called adjuvants or additional shots called boosters to help the body remember the vaccine. Making these vaccines also takes longer because the pathogens need to be grown and then killed. Sometimes, people need several doses over time to stay protected, which can be challenging for public health programs. For example, the flu vaccine needs updates and re-administration every year.