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Pertussis Outbreak in Infants and an Immunization Campaign Based on Providing Pertussis Vaccine Doses at 6 Weeks, 10 Weeks, and 14 Weeks

Stein-Zamir, Chen, MD, PhD, MPH; Sokolov, Irina, MD, MPH; Abramson, Nitza, MD, MPH; Shoob, Hanna, MPH

The Pediatric Infectious Disease Journal: March 2019 - Volume 38 - Issue 3 - p e63–e64
doi: 10.1097/INF.0000000000002122
Letters to the Editor
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Jerusalem District Health Office, Ministry of Health, Israel, Faculty of Medicine, The Hebrew University and Hadassah Braun School of Public and Community Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel

Jerusalem District Health Office, Ministry of Health, Israel

The authors have no funding or conflicts of interest to disclose.

Address for correspondence: Chen Stein-Zamir, MD, PhD, MPH; E-mail: chen.zamir@lbjr.health.gov.il.

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To The Editors:

Bordetella pertussis infections are associated with considerable disease burden.1 The highest pertussis incidence rates in Israel are observed among infants.2–4 The routine schedule includes acellular pertussis (aP) vaccine at 2-4-6 and 12 months; DTaP4 coverage rates are 94%–95%.2–4

Pertussis notifications increased markedly in the Jerusalem district in 2015 (1.1 million residents, 12.8% children younger than 5 years of age and 2.8% infants younger than 1 year of age). Overall, 1084 pertussis cases were notified in the Jerusalem district (in all age groups) in 2015 compared with 383 cases in 2014. The overall pertussis incidence rate increased from 38/100,000 population in 2014 to 104/100,000 population in 2015. The peak incidence rate was in infants younger than 1 year of age, 361/100,000 (2015), compared with 58/100 000 in toddlers 1–4 years of age. Infants (n = 104) were 9.6% of pertussis cases; the median age was 2.6 months (11.3 weeks); 57% males. Infants accounted for most hospitalizations (87%) and all deaths (n = 3). The hospitalized infants (n = 41) were younger, median age 1.4 months (6.1 weeks), mean hospital stay of 6.6 ± 6.4 days; 8 infants required pediatric intensive care unit treatment. The main symptoms were cough with or without whoop, respiratory distress (62%), posttussive vomiting (34%) and apnea (26%). Supplemental oxygen and artificial ventilation were required in 39% and 9%, respectively. The mean peripheral leukocyte count was 23.6 ± 11.8 (×109/l). Case confirmation in 92% was by polymerase chain reaction. Mortality occurred in a 7-week-old and an 8-week-old infants; both were healthy females, unvaccinated (as to age), presented with 2-week cough, vomiting and dyspnea; pediatric intensive care unit life support and extracorporeal membrane oxygenation failed. A 9-month-old male with multiple congenital anomalies (unvaccinated) was admitted with cough, apnea and cyanosis and died after 9 days of hospitalization.

Vaccination status of the infants is as follows: 69 infants were unvaccinated (42 infants younger than 2 months of age); 21, 12 and 2 infants had received 1, 2 and 3 pertussis vaccine doses, respectively. Two mothers received third-trimester pertussis vaccine (pertussis vaccination in pregnancy was included in the national health insurance basket in Israel in 2015).

An immunization campaign including widespread distribution of information, mass catch-up immunizations and outreach activities in the Jerusalem district started during May 2015. An accelerated pertussis vaccination schedule at 6, 10 and 14 weeks of age was implemented, targeting infants who were born in April–June 2015 (n = 7855). The DTaP1 coverage before 2 months of age was 54% (born April–June 2015) versus 7.9% (born April–June 2014). For DTaP2 before 4 months of age, the fraction was 55% versus 5% (P = 0.0001). Pertussis notifications and incidence rates per 100,000 in infants younger than 1 year of age are presented in Figure 1 (2010–2017, Jerusalem district). The pertussis incidence rate in infants declined 82%, from 618/100,000 (January–June 2015) to 111/100,000 (July–December 2015) after the immunization campaign (P = 0.001). A slighter decline was noted in the district’s other age groups (35%) during July–December 2015. In prior endemic years (2011–2012), immunization campaigns were performed, keeping the 2-4-6 months’ vaccination schedule with a more gradual decline. The Jerusalem district’s residents comprised 14% of Israel’s population in 2015. The district’s fraction of pertussis notifications nationally (2010–2014) was 18.6%, increased to 29.9% in January–June 2015, declined to 11.4% in July–December 2015 (P = 0.0001) post the campaign, and during 2016–2017, it was 12.7%.

FIGURE 1

FIGURE 1

The immunization campaign focused on young infants. While the cases’ median age (2.6 months) was similar to previous reports (2.7 and 2.9 months), hospitalized infants were younger, median age 6.1 weeks versus 9.6 and 7.9 weeks.3,4 The World Health Organization guidelines include a 3-dose series, 6, 10–14 and 14–18 weeks.5 The 6-10-14 weeks schedule showed the highest potential impact on pertussis incidence in infants (36% advantage on 2-4-6 months).6 Moreover, the accelerated schedule improved DTaP-IPV-Hib1 (Diphtheria-Tetanus-acellular Pertussis-Polio-Haemophilus influenzae type b, first dose) vaccine timeliness, which had been found predictive for future vaccination status.7 In conclusion, modifying the 2-4-6 months’ to the 6-10-14 weeks’ vaccination schedule was found feasible in a high disease burden situation in young infants. The observed incidence decline requires further research.

Chen Stein-Zamir, MD, PhD, MPH

Jerusalem District Health Office

Ministry of Health

Israel

Faculty of Medicine

The Hebrew University and Hadassah Braun School of Public and Community Medicine

The Hebrew University of Jerusalem

Jerusalem, Israel

Irina Sokolov, MD, MPH

Nitza Abramson, MD, MPH

Hanna Shoob, MPH

Jerusalem District Health Office

Ministry of Health

Israel

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REFERENCES

1. Tan T, Dalby T, Forsyth K, et al. Pertussis across the globe: recent epidemiologic trends from 2000 to 2013. Pediatr Infect Dis J. 2015;34:e222–e232.
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3. Stein-Zamir C, Shoob H, Abramson N, et al. The impact of additional pertussis vaccine doses on disease incidence in children and infants. Vaccine. 2010;29:207–211.
4. Zamir CS, Dahan DB, Shoob H. Pertussis in infants under one year old: risk markers and vaccination status–a case-control study. Vaccine. 2015;33:2073–2078.
5. World Health Organization. Pertussis vaccines: WHO position paper, August 2015–Recommendations. Vaccine. 2016;34:1423–1425.
6. Bergero PE, Fabricius G, Hozbor DF, et al. Potential impact of changes in the schedule for primary diphtheria-tetanus toxoids-pertussis immunization as control strategy for pertussis. Pediatr Infect Dis J. 2018;37:e36–e42.
7. Stein-Zamir C, Israeli A. Age-appropriate versus up-to-date coverage of routine childhood vaccinations among young children in Israel. Hum Vaccin Immunother. 2017;13:2102–2110.
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