Effectiveness of the 13-Valent Pneumococcal Conjugate Vaccine on Invasive Pneumococcal Disease in Greenland

Abstract

The 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in 2010 to the childhood vaccination program in Greenland. This study aimed to estimate the effectiveness of the PCV13 on the incidence of invasive pneumococcal disease (IPD) in children and in adults in Greenland. IPD cases from the pre-PCV13 period (January 1995–September 2010) were compared with the post-PCV13 period (September 2010–October 2020). Register data were collected from laboratory records, IPD reports, the national registry on admissions, and medical files. A total of 295 IPD cases were identified in the study period. Overall IPD incidence rate (IR) declined from the pre-PCV13 period to the post-PCV13 period (IR 23.3 to 15.3 per 100,000 person years). Overall IPD incidence among children decreased significantly, whereas overall IPD incidence among the elderly increased significantly. During the post-PCV13 period, the incidence of vaccine serotype (VT) IPD decreased in all ages, while the incidence of non-vaccine serotype (NVT) IPD increased. This increase was most substantial among elderly ≥ 60 years. In conclusion, the PCV13 has reduced incidence rates of IPD in Greenland. However, the increase in NVT IPD among the elderly is noteworthy, and sup-ports continued surveillance of IPD in the population of Greenland.

Mortality of Invasive Pneumococcal Disease following Introduction of the 13-Valent Pneumococcal Conjugate Vaccine in Greenland

“…This surveillance system has confirmed high rates of IPD in other Inuit populations [ 5 ]. Yet, few studies have evaluated the burden of IPD in the Inuit population of Greenland [ 3 , 6 , 7 , 8 ].…”

“…The CVP is free and is eligible to all children with a permanent address in Greenland [ 10 ]. Before the introduction of the PCV13, IPD rates among Inuit in Greenland were up to four times higher than among non-Inuit in the country [ 6 , 8 ].…”

“…In our previous study [ 8 ], it was shown, that after the introduction of the PCV13, the overall incidence of IPD declined with 30% and IPD caused by vaccine serotype (VT) declined with 55%. Moreover, VT-IPD incidence rates among children ≤1 years declined with 30%, and no VT-IPD cases among children 2–4 years were observed post-PCV13 introduction.…”

“…The indirect vaccine protection of persons older than the targeted group for vaccination has shown to be due to reduced carriage of S. pneumoniae in the vaccinated persons, thereby reducing the transmission of the infection [ 2 ]. However, as in many other countries, the introduction of the PCV13 in Greenland has been associated with shifts in nasopharyngeal pneumococcal serotype distribution with increased carriage of non-vaccine serotypes (NVT), increasing NVT-IPD incidence rates among adults ≥60 years [ 8 ].…”

“…While our previous study demonstrated the effect of PCV13 on serotype distribution in Greenland [ 8 ], little is known regarding the effect of pneumococcal conjugate vaccines (PCVs) on IPD-related mortality, particularly in Greenland.…”