The Australian government announced last week there’s a new vaccine for pneumococcal disease on the National Immunisation Program for all children.

This vaccine replaces previously listed pneumococcal vaccines, having been updated to offer better protection against the disease.

So what is pneumococcal disease? And what is this new vaccine?

From meningitis to ear infections

Pneumococcal disease encompasses a range of infections caused by the common bacterium Streptococcus pneumoniae, also known as pneumococcus.

Anyone can get pneumococcal disease. However, it’s more common in young children, older people, those with weakened immune systems and certain medical conditions.

The most severe forms of pneumococcal disease are meningitis (inflammation around the brain) and bacteraemia (a bloodstream infection). These are often referred to as invasive pneumococcal disease and can be life-threatening.

Pneumococcus is also responsible for most hospitalisations for bacterial pneumonia, a particular problem in young children and older adults. Another common condition pneumococcus causes in children is middle ear infections (otitis media).

There are more than 100 different strains (called serotypes) of pneumococcus. Some strains frequently cause disease in humans, while others rarely do.

In healthy people, particularly preschool children, pneumococcus can be found in the back of the nose. Often it’s just sitting there, without causing illness – this is known as colonisation. Individuals who are colonised with pneumococcus, particularly young children, spread the bacteria, usually through respiratory droplets.

Invasive pneumococcal disease can occur when a person acquires a new strain and the bacteria travels from the nose to a part of the body where it’s not normally found.

In Australia, health professionals and laboratories must notify state health departments when they encounter cases of invasive pneumococcal disease, and strain data is collected. There were about 2,400 cases reported in 2024, with one-fifth in children.

Pneumococcal vaccines

Vaccines are designed to simulate the natural immune response following infection, ensuring the recipient’s immune system can promptly respond when exposed.

The outer coating of the pneumococcus, called its polysaccharide capsule, is key to our body’s immune response to the bacteria. So pneumococcal vaccines induce immunity against the selected strains’ polysaccharide capsules.

Pneumococcal vaccines have been around for more than 100 years, and have changed and advanced many times.

Current pneumococcal vaccines are multivalent, meaning they protect against multiple strains. Those strains with the greatest tendency to cause disease are chosen to be included.

One type of pneumococcal vaccine is a pneumococcal polysaccharide vaccine, or PPV. A vaccine containing polysaccharide from 23 different strains (23-valent or 23vPPV) has been recommended to certain Australian children at higher risk from pneumococcal until now.

But while this vaccine provides protection against many strains, these PPVs provide only short-term protection.

Newer vaccines

Pneumococcal conjugate vaccines (PCVs) were developed more recently to achieve a stronger immune response. In PCVs, the polysaccharide is linked to a carrier protein, which stimulates other components of the immune system, providing better and longer-lasting protection.

The first PCV to be used in childhood vaccination programs across many countries contained seven strains (7vPCV). This vaccine was first given to all Australian children through the National Immunisation Program in 2005.

Over the years new PCVs were developed, incorporating more strains. In 2011, 13vPCV replaced 7vPCV in Australia’s pneumococcal vaccination program.

Real-world data showed these PCVs were around 90% effective at preventing invasive pneumococcal disease from the targeted strains in Australian children.

But like many bacteria and viruses, pneumococcus continues to evolve. Two new PCVs (15vPCV and 20vPCV) were licensed for use in Australia in recent years.

Based on advice from the Australian Technical Advisory Group on Immunisation, the PCV offered to children on the National Immunisation Program was switched on September 1 from 13vPCV to 20vPCV.

Efficacy and safety

In multiple clinical trials, 20vPCV produced comparable immune responses against the 13 strains it has in common with 13vPCV. It also elicited good immune responses against all seven extra strains.

With its additional strains, 20vPCV is expected to prevent 25–30% more cases of invasive pneumococcal disease in children compared to 13vPCV. It will also prevent more cases of less severe pneumococcal infections such as pneumonia and otitis media in children.

The hidden power of PCVs is they prevent disease in the wider population beyond vaccinated children by reducing pneumococcal colonisation and thereby transmission. These indirect benefits should result in fewer cases of pneumococcal disease overall, including in unvaccinated children and adults.

Trials also showed the 20vPCV has a similarly good safety profile to 13vPCV, which has been used for more than 15 years with no serious concerns.

The World Health Organization recommends PCVs should be part of all routine childhood immunisation programs. This is now the case in 160 countries.

When do children get this vaccine?

The dosing schedule for pneumococcal vaccines has been modified over time in Australia to optimise protection.

Most recently, three doses of 13vPCV were recommended for all children at two, four and 12 months old. An extra dose was given at six months to those at increased risk of pneumococcal disease including Aboriginal and Torres Strait Islander children in certain states and territories, and children with underlying medical risk factors.

In addition to four doses of 13vPCV, up to two doses of the older 23vPPV vaccine were given to Aboriginal and Torres Strait Islander children in certain jurisdictions and children with underlying medical risk conditions to extend protection to more strains.

With the transition to 20vPCV, 13vPCV will be replaced and 23vPPV is no longer required in children, as 20vPCV sufficiently covers all strains currently causing disease.

Three 20vPCV doses are recommended for all infants (at two, four and 12 months). An extra dose at six months is recommended for all Aboriginal and Torres Strait Islander children nationally (not just those in selected jurisdictions) and children with specified medical risk conditions.

Children who have been partially vaccinated so far (that is, have received one or two doses of 13vPVC) can complete their routine schedule with 20vPCV without extra doses.

These changes broaden the protection offered and simplify pneumococcal vaccine recommendations. While nine in ten children receive three or more doses of pneumococcal vaccine, it’s hoped these changes will lead to even better compliance from both parents and providers, and fewer cases of pneumococcal disease.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Christopher Blyth, The University of Western Australia and Sanjay Jayasinghe, University of Sydney

Read more:

Chris Blyth receives funding from National Health and Medical Research Council (NHMRC) and Medical Research Future Fund. He is on the board of the Australasian Society for Infectious Diseases. He has previously been a member of the Australian Technical Advisory Group on Immunisation.

Sanjay Jayasinghe receives funding from National Health and Medical Research Council (NHMRC) and Medical Research Future Fund (MRFF). He is currently the Chair of the Enhanced Invasive Pneumococcal Disease Surveillance Working Group of Communicable Diseases Network Australia.