Information on pneumococcal conjugate vaccine efficacy found in the Prevnar 13(PCV13) product insert reports information pertaining to the original PCV vaccine, Prevnar (PCV7). PCV7 was reported to be 100 percent effective at preventing invasive disease caused by S. pneumoniae during the pre-licensing clinical trial which took place over a 34-month period. An eight-month extended follow-up of vaccine recipients reported the vaccine’s efficacy to be between 93 and 97.4 percent.
In clinical studies pertaining to the PCV vaccine for the prevention of acute otitis media, studies found PCV7 to be only seven percent effective at preventing acute otitis media and children who received PCV7 were noted to be at a higher risk for developing acute otitis media from strains not covered by the vaccine. Studies also found that PCV7 reduced the need for tympanostomy tubes (ear tubes) by 20 percent.
One large scale study involving nearly 85,000 adults 65 years of age and older found PCV13 to be 45.6 percent effective against vaccine-type pneumococcal pneumonia, 45 percent effective against vaccine-type non-bacteremic pneumococcal pneumonia and 75 percent effective against all vaccine-type invasive pneumococcal disease.
The Prevnar 13 (PCV13) product insert also states that effectiveness of the vaccine cannot be established in the following population:
- Infants born prematurely
- Persons with HIV-infection
- Children with sickle cell disease
- Persons who had received an allogeneic hematopoietic stem cell transplant
Following FDA approval of the first pneumococcal conjugate vaccine, Prevnar (PCV7), researchers discovered that while the vaccine was effective in reducing the risk of infection caused by the seven strains found within the vaccine, strains not found within the vaccine began to emerge and increase in prevalence. Most notably, strain 19A, a highly virulent strain resistant to all antibiotics FDA approved for use in children for the treatment of acute otitis media, emerged.
In addition to pneumococcal strain replacement, the introduction of PCV7 resulted in a significant increase in pneumococcal empyema, a complication of pneumococcal pneumonia resulting in an accumulation of pus between the lungs and the inner aspect of the chest wall. The most common strains causing empyema were found to be pneumococcal strains 1, 3 and 19A, three strains not covered in the PCV7 vaccine.
While invasive disease from vaccine-type strains decreased significantly within the first four years following the introduction of PCV7, antibiotic resistant non-vaccine type strains began to take their place. In one particular population of Alaska Native children, the introduction of the PCV7 vaccine caused a 140 percent increase of invasive pneumococcal disease from strains not found in the vaccine.
Rates of pneumococcal meningitis by antibiotic resistant strains not found in the PCV7 vaccine continued to increase, which prompted researchers to emphasize the need for better pneumococcal vaccines.
The 2010 introduction of PCV13 vaccine, adding six additional strains to the original PCV7, resulted in a further decline of invasive pneumococcal disease. However, PCV 13 vaccine has not been completely effective in eliminating vaccine-strain invasive pneumococcal disease and serious infections have persisted despite the licensing of a broader vaccine.
In addition to the vaccine’s ineffectiveness in eliminating pneumococcal disease from all strains contained within the vaccine, non-vaccine type strains have also emerged in the United States, most notably strains 33F, 22F, 12, 15B, 15C, and 23 A. Other countries have experienced a similar situation, including Taiwan, which noted a decrease in vaccine-type strain invasive disease and confirmed pneumococcal disease but an increase in non-vaccine type strain invasive disease, most notably caused by strains 23A, 15A and 15B.
Korea has also reported high rates of antibiotic-resistant strains not found in PCV13 since the introduction of the vaccine. Non-vaccine type strains continue to appear in many Western European countries, prompting researchers to stress the need for new vaccines to cover the antibiotic-resistant strains of S. pneumoniae not found within the current vaccines.
Researchers in the United States have noted that while invasive pneumococcal disease has decreased since the introduction of pneumococcal conjugate vaccines, S. pneumoniae strains have continued to adapt and this has resulted in the ongoing emergence of antibiotic resistant non-vaccine serotypes.
The use of pneumococcal conjugate vaccines has also caused an increase in other serious pathogens such as Haemophilus influenzae and Moraxella catarrhalis. Since the introduction of PCV vaccines, H. influenzae and M. catarrhalis otitis media have increased to replace S.pneumoniae otitis media.
While the CDC and other global health organizations have attributed the decrease in invasive pneumococcal disease to vaccination, the introduction of pneumococcal conjugate vaccines has brought changes to clinical practice. Emergency room collection of blood cultures, once a routine practice in the assessment and treatment of children presenting with fever in the emergency room, have decreased since PCV vaccine introduction. This change in clinical treatment protocol may be obscuring the ability to detect vaccine and non-vaccine strains of pneumococcal disease in children.
A study of Aboriginals living in Western Australia found that while PCV7 vaccination decreased the number of vaccine-type invasive pneumococcal infections in the elderly and young children, it significantly increased the amount of non-vaccine type pneumococcal diseases in adults.
Another study involving a similar population in Australia found that vaccine strain pneumococcal disease was not replaced by non-vaccine strain disease in children but non-vaccine strain disease rose significantly in adults. This offset any potential benefit that vaccination might have had on the adult population.
At the CDC’s October 2018 ACIP meeting, public health officials reported that vaccinating all persons 65 and older with PCV13 has had no impact on reducing the rates of both invasive and non-invasive pneumococcal disease. In June 2019, ACIP voted to pull back from its 2014 routine recommendation and stated that healthy seniors 65 and older could consider vaccination with PCV13 after discussions with their physician. PCV13 was still recommended for seniors 65 years and older who have chronic health conditions and a single dose of PPSV23 was still recommended for all persons 65 and older.
