The herd effects of infant PCV7/PCV13 sequential implementation on adult invasive pneumococcal disease, six years post implementation; a nationwide study in Israel.
Introduction of pneumococcal conjugate vaccine (PCV) has nearly eliminated vaccine-type (VT) invasive pneumococcal disease (IPD) in children, yet the reported resulting reduction of adult IPD is variable. We present the indirect impact of sequential PCV7/PCV13 implementation in Israel on adult IPD.



An ongoing nationwide active surveillance was initiated on July 2009 when PCV7 was implemented (with Catch-up). PCV7 was gradually replaced by PCV13 since November 2010. Comorbidity and outcome data were collected from medical files. Incidence rates were calculated for overall and vaccine-type IPD.



A total of 2579 IPD cases were diagnosed among a population of 5.0-5.5 million adults >18y (2009-2015). Incidence rates were 9.15/100,000 and 10.16/100,000 in the first and second study years, respectively. However, after PCV13 implementation, the rates decreased to 7.19 within four years, and remained stable in the two following years. Within 6years, PCV7-VT-IPD incidence decreased from 2.52 to 0.52 (79%) and PCV13-VT-IPD from 6.15 to 1.81 (71%). Concurrently, non-VT13 incidence increased from 2.99 to 5.25. Approximately 50% of all patients were adults ≥65y, in whom the decrease in PCV13-VT-IPD incidence was smaller and slower (65% vs. >80% decrease in adults <50y).



Despite continued reduction in PCV13-VT-IPD, overall IPD was stable during the last two years due to serotype replacement. Yet, the significant decrease in adult IPD, six years post-PCV7/13 implementation emphasizes the importance of indirect protection in achieving overall population impact and should be considered when discussing the potential additional benefits of direct adult PCV vaccination.
Sheba Med Ctr, Ramat-Gan, Israel; Tel-Aviv University, Tel-Aviv, Israel. Electronic address: gili.regev.y@gmail.com.
Gili
G
Regev-Yochay
Tel-Aviv University, Tel-Aviv, Israel; Meir Med Ctr, Kfar Saba, Israel.
Michal
M
Katzir
Haddassah Med Ctr, Jerusalem, Israel.
Jacob
J
Strahilevitz
Sheba Med Ctr, Ramat-Gan, Israel; Tel-Aviv University, Tel-Aviv, Israel.
Galia
G
Rahav
Tel-Aviv University, Tel-Aviv, Israel; Tel-Aviv Med Ctr, Tel-Aviv, Israel.
Talya
T
Finn
Rivka Ziv Med Ctr, Sefed, Israel.
Dan
D
Miron
Tel-Aviv University, Tel-Aviv, Israel; Wolfson Med Ctr, Holon, Israel.
Yasmin
Y
Maor
Emek Med Ctr, Afula, Israel.
Bibiana
B
Chazan
Maayanei Hayeshua Hosp, Bnei-Brak, Israel.
Yehudith
Y
Schindler
Ben-Gurion University, Beer-Sheva, Israel.
Ron
R
Dagan
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002675:Child, Preschool; D062665:Epidemiological Monitoring; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine / Q000008:administration & dosage* / Q000276:immunology*; D006801:Humans; D032521:Immunity, Herd; D015994:Incidence; D007223:Infant; D007557:Israel / Q000453:epidemiology; D008297:Male; D016920:Meningitis, Bacterial / Q000453:epidemiology; D008875:Middle Aged; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D011446:Prospective Studies; D018805:Sepsis / Q000453:epidemiology; D055815:Young Adult
C538862:13-valent pneumococcal vaccine; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022242:Pneumococcal Vaccines
13-Valent pneumococcal conjugate vaccine impact; Adult invasive pneumococcal disease; Herd effect; Nationwide active surveillance; Serotype replacement