Pneumococcal vaccine

A shot helps keep you safe from germs.

It stops some sicknesses in the body. There are two kinds of shots. One kind is very good for young kids.

The other kind is for adults. These shots are given with a small needle. They can go into a muscle. They can also go under the skin. Most people stay safe and well after the shot.

A pneumococcal vaccine is a shot that protects people. It helps fight a germ called Streptococcus pneumoniae. This germ can cause serious sicknesses. These include pneumonia, meningitis, and sepsis.

There are two main types of these vaccines. One type is called a polysaccharide vaccine. This type works well for healthy adults. However, it does not work for children under two years old. The other type is a conjugate vaccine. This type is very strong. It helps the body build long-lasting memory. This means the body remembers how to fight the germ later. The World Health Organization says kids should get this type.

Doctors give these shots with a needle. They go into a muscle or under the skin. Most people stay safe after the shot. Some babies might get a fever or redness where they were poked. These shots are very important. They help stop germs from spreading to others. This is called herd immunity. It helps keep the whole community healthy.

Pneumococcal vaccines are special shots that protect people from a germ called Streptococcus pneumoniae. This bacterium can cause very serious sicknesses like pneumonia, meningitis, and sepsis. Because these illnesses can be dangerous, scientists have worked hard to create ways to stop them. There are two main types of these vaccines used by doctors today. One type is called a polysaccharide vaccine, which works well for healthy adults. The other is the conjugate vaccine, which is a much stronger version. The World Health Organization recommends using the conjugate vaccine for children to keep them safe.

These vaccines work in different ways to teach the body how to fight. The polysaccharide vaccine works by stimulating B-cells, which are parts of our immune system. However, this type does not help the body create memory cells or protect the lungs. This is why it does not work for children under two years old. The conjugate vaccine is different because it attaches parts of the germ to a protein called CRM197. This protein helps recruit helper T cells to join the fight. These cells allow the body to create memory B cells and long-lasting immunity.

People have been studying these germs for a long time. Scientists began identifying different types of pneumococcus in the early 1900s. The very first polysaccharide vaccine, which was tetravalent, was developed in 1945. Later, in the 1980s, scientists created the 23-valent polysaccharide vaccine. The first conjugate vaccine, known as the heptavalent version, reached the market in the year 2000. Since then, new versions have been made to cover even more types of the germ. These updates help fight germs that have become resistant to medicines.

There are many specific numbers and dates to know about these tools. In the United States, the 23-valent vaccine was approved in 1983. A newer conjugate vaccine called Prevnar 20 was approved in June 2021. In South Africa, using these vaccines helped lower disease rates in children by nearly 70%. The conjugate vaccine is often 71% to 93% effective at preventing severe disease. Some vaccines, like the 23-valent version, protect against 23 different types of the germ. These include many types that are known to be drug-resistant.

Understanding these vaccines helps us see how we protect whole communities. When many people get vaccinated, it creates something called herd immunity. This means the germ has a hard time spreading from person to person. This protects people who might not be able to get the shot themselves. Programs like PneumoADIP work to get these vaccines to more people in the developing world. Organizations like GAVI help make sure these medicines are affordable for many countries. By working together, we can use science to keep more children healthy around the world.

Pneumococcal vaccines are specialized subunit vaccines designed to protect humans against the bacterium Streptococcus pneumoniae. This bacterium is responsible for several serious medical conditions, including pneumonia, meningitis, and sepsis. Because these diseases can be life-threatening, vaccines are a vital tool in global public health. There are two primary categories of these vaccines: polysaccharide vaccines and conjugate vaccines. These are administered via injection into either a muscle or the area just under the skin. The World Health Organization (WHO) specifically recommends conjugate vaccines for routine childhood immunizations, including for children living with HIV/AIDS.

To understand how these vaccines function, we must look at how they interact with the immune system. Polysaccharide vaccines consist of purified polysaccharides from 23 different serotypes, which are specific strains of the bacteria. These vaccines work by stimulating B-cells to release IgM antibodies. However, this process does not involve T cells, making the immune response less robust. Because they do not provoke mucosal immunity, they do not reduce how many people carry the bacteria or protect the respiratory tract. This lack of a strong response is why polysaccharide vaccines are ineffective in children under two years old or in people with poor immune function.

Conjugate vaccines, or PCVs, use a different and more complex mechanism to build immunity. These vaccines consist of capsular polysaccharides that are covalently bound to a protein called CRM197. This protein is highly immunogenic, meaning it triggers a strong response, but it is non-toxic to the patient. By attaching the sugar coating of the bacteria to this protein, the vaccine recruits CRM197-specific type 2 helper T cells. This recruitment allows the body to undergo immunoglobulin type switching to produce more than just IgM. Crucially, this process creates memory B cells, which leads to mucosal immunity and long-lasting, lifelong protection after several exposures.

The development of these vaccines has spanned over a century of scientific discovery. Researchers began characterizing the different subtypes of pneumococcus in the early 1900s. The first polysaccharide vaccine, which was tetravalent, was developed in 1945. By the 1980s, scientists had developed the 23-valent polysaccharide vaccine. The first conjugate vaccine, a heptavalent version, reached the market in the year 2000. Since then, new versions have been released to cover more serotypes and combat antibiotic-resistant strains. For example, the 13-valent conjugate vaccine (PCV13) was introduced in 2010, and the 20-valent version (PCV20) was approved in 2021.

Vaccination efforts have produced significant, measurable results in public health statistics. In South Africa, the introduction of PCV7 and PCV13 led to a massive decline in invasive pneumococcal disease (IPD). Among children under two, the overall incidence of IPD fell by nearly 70%. Furthermore, the rates of IPD caused by bacteria specifically targeted by the vaccine dropped by nearly 90%. The conjugate vaccine itself is highly effective, showing a 71% to 93% success rate in preventing severe disease when three or four doses are given. The 23-valent polysaccharide vaccine also shows high protective efficacy, ranging from 76% to 92% for the 23 most prevalent types.

Global health organizations use various strategies to ensure these vaccines reach those in need. The PneumoADIP program works to accelerate the evaluation and access to new vaccines in the developing world. This program is funded by the Global Alliance for Vaccines and Immunization (GAVI). To address the lack of affordable vaccines, GAVI launched a pilot Advance Market Commitment (AMC) in June 2009. Under an AMC, donors provide a legally binding guarantee to purchase a set amount of vaccines at an agreed price if they meet safety standards. This strategy aims to create a guaranteed market for manufacturers while ensuring affordability for developing nations. The AMC was estimated to prevent more than 1.5 million childhood deaths by 2020.

However, the implementation of these programs has faced some criticism and complexity. Doctors Without Borders has argued that the AMC model might not encourage enough innovation or competition. They noted that the system allowed a duopoly between Pfizer and GlaxoSmithKline, which made it harder for cheaper options, like those from the Serum Institute of India, to enter the market. This resulted in price discrimination, where middle-income countries faced prices about ten times higher than those paid by GAVI-supported nations. Despite these challenges, the vaccines remain essential. The conjugate vaccine's ability to reduce colonization rates also provides herd immunity, protecting even those who are not vaccinated by breaking the chain of transmission.