The vaccines protect against the more common bacterial strains responsible for pneumococcal disease, which causes a range of infections including pneumonia, meningitis, sinus and middle-ear infection. It can lead to very severe illness and even death.
In fact, pneumonia, or inflammation of the lungs, is the third major cause of death here.
These vaccines do not protect against all causes of pneumonia, since that can be due to a range of bugs including other types of bacteria, virus or even fungi.
But they do provide protection against the more common strains of the Streptococcus pneumoniae bacteria, which is why the Government encourages and subsidises pneumococcal vaccination for Singaporean children and seniors.
For seniors, the recommendation is to get the pneumococcal conjugate PCV13 vaccine first, followed by the pneumococcal polysaccharide PPSV23 vaccine a year later.
The new vaccine, PCV20, covers seven more bacterial strains than the PCV13, also manufactured by Pfizer. The PPSV23 is by Merck Sharp & Dohme and covers 23 strains of bacteria.
Professor Julio Ramirez, chief research scientist at the Norton Infectious Diseases Institute at Norton Healthcare in the United States, who was the principal investigator in studies of the PCV13 vaccine, was brought in by Pfizer for the launch of the PCV20 here on Saturday.
He said that unlike polysaccharide vaccines, conjugate vaccines, aside from getting the body to produce antibodies that protect against infection, also prime T cells and memory B cells, which can mount a response against invasive bacteria even after the level of antibodies has waned.
Professor Ooi Eng Eong, a microbiologist at the Duke-NUS Medical School, also said the immune responses from a conjugate vaccine “would theoretically be broader and more lasting than what is elicited by polysaccharides alone”.
Associate Professor Lim Poh Lian, who heads the Travellers’ Health and Vaccination Clinic at Tan Tock Seng Hospital and is also a senior consultant at the National Centre for Infectious Diseases, said: “Conjugate vaccines like PCV13 or PCV20 are better able to stimulate an immune response compared to the polysaccharide vaccine PPSV23, which was the reason conjugate vaccines were developed.”
Associate Professor Hsu Liyang, an infectious diseases specialist at the National University of Singapore Saw Swee Hock School of Public Health, said the newer vaccine can certainly replace the PCV13.
“It is also possible that the use of this vaccine can obviate the need for the use of the 23-valent polysaccharide vaccine,” he added.
Agreeing, Prof Lim said: “For those who have not had the PCV13 and PPSV23 combination yet, having a single dose of PCV20 greatly simplifies the vaccination regimen for patients and families. Instead of trying to sequence two vaccines with all the other health visits, this vaccine allows them to just get ‘one and done’.”
While Dr Asok Kurup, who chairs the Chapter of Infectious Disease Physicians, agrees that the wider coverage from PCV20 can mean just a single dose for the vast majority, he said people at higher risk, such as the immunocompromised, should still get the PPSV23 as well, as it covers more strains.
The Ministry of Health (MOH) told The Straits Times that while the new vaccine has been approved for use here since November 2022, a review is on to decide “whether the vaccine should be recommended for inclusion in the national immunisation schedules”.
If it is not, there will be no subsidy for its use.
Prof Lim said the Expert Committee on Immunisation is assessing the clinical- and cost-effectiveness of PCV20 and how it should be used.
Dr Kurup said that in the private sector, the PPSV23 costs just under $100 and PCV13 about $200. The price of PCV20 should be about the same as that of PCV13, he added.
An MOH spokesman said those who have been recommended to receive the PCV13 and PPSV vaccines under the National Adult Immunisation Schedule are advised to do so. The PCV20 is currently not for use in children.
The infectious diseases experts ST spoke to agree that people who have received the two pneumococcal vaccines do not need to get the PCV20 as well.
Professor Paul Tambyah, a senior infectious diseases consultant at the National University Hospital, said: “The big question to me is whether PCV20 will be replaced by PCV25.”
An ongoing study for a 25-valent pneumococcal conjugate vaccine, which started in 2022, is expected to be completed by 2025.
According to thestar.com.my