From Sea to Shining Sea Pertussis Outbreaks Across the Nation

According to the CDC, starting late in spring 2018 and continuing today, clinicians have been reporting nationwide outbreaks of pertussis, also known as whooping cough.

In fact, the outbreaks have become a staple of the nightly news, as public health officials attempt to get the word out that pertussis is a serious disease with potentially deadly implications for at-risk populations.^1-5 The availability of effective vaccines reduced the number of pertussis cases significantly starting in the late 1940s; nevertheless, beginning in 2012, the CDC began to see an uptick in whooping cough cases. Often, these outbreaks occurred in or near antivaccination communities that avoided or delayed vaccines for infants and young children.⁶ The current outbreak, however, is probably related to the waning immunity and the inadequate reimmunization (booster shots) in adults and teens, according to the CDC.^7,8 For facts about pertussis, see Table 1.^7-9

To understand what is going on with the current outbreak, pharmacists need to know a little bit about the history of the pertussis vaccine. Traditionally, health care professionals have administered the vaccine in the combination product for diphtheria, tetanus, and acellular pertussis (DTaP). The shot series begins at 2 months of age, followed by boosters at 4, 6, and 9 months. Notice that if the vaccine is administered as recommended, infants have a protection “hole” during the first month of life, before detectable immunity develops. These infants are at the highest risk of death from pertussis. Children are not completely immune until they receive 3 shots in the recommended series. Thus, pertussis is especially dangerous for children younger than 2 years if they haven’t followed the proper schedule.^10-12

The most likely way for unprotected children to contract pertussis is through contact with unimmunized adults who often have a milder or even an unrecognized form of the disease. For this reason, the CDC has recommended that pregnant women receive a booster in the third trimester. Once the pregnant woman develops pertussis antibodies, she transmits them to her unborn child, providing some pertussis immunity early in the child’s life.^13,14

So why are we experiencing outbreaks now?

The original diphtheria, tetanus, and pertussis vaccine became available in the United States in 1948, and the number of whooping cough cases dropped from 260,000 in 1934 to just a few thousand annually by the 1990s. This vaccine was “whole-cell” pertussis, which included all the antigens of the pertussis bacterium. At the time, investigators did not understand, and still do not fully understand, which pertussis antigens induce the proper immune response. Public health officials noticed rare adverse effects, including convulsions, which occurred in 1 of 1750 cases, and acute encephalopathy in about 0 to 10.5 cases per million doses. These safety concerns led investigators to develop a more purified “acellular” pertussis component, containing fewer antigens but still invoking an immune response. In 1997, the Advisory Committee on Immunization Practices recommended the acellular pertussis vaccine as the preferred vaccine. The actual switch began in 1991, and by 1999, nearly all children were immunized using the acellular version.⁷

It became clear that the whole-cell pertussis vaccine provided protection over much longer duration. Protection from the acellular vaccine tends to wane over time.

The CDC reports that initially, 80% to 90% of children who receive 5 doses of the tetanus, diphtheria, and acellular pertussis vaccine will be protected, but that protection drops to 70% 5 years after their last shot and to only 30% to 40% at 10 years. This means practitioners need to increase vigilance and ensure that adults and children receive their booster shots.^14,6

Preventing Infection Spread

The CDC has issued postexposure prophylaxis recommendations (see Table 2), and pharmacists need to be aware of them, especially if they provide care for families who choose not to vaccinate.^6,15

Jeannette Y. Wick, RPh, MBA, FASCP, is an assistant director of the Office of Pharmacy Professional Development at the University of Connecticut School of Pharmacy in Storrs.

References

• DPH investigating outbreak of whooping cough in Kent County; urging residents to get vaccinated [news release]. Dover, DE: Delaware Health and Social Services, Division of Public Health; August 23, 2018. news.delaware.gov/2018/08/23/dph-investigating-outbreak-whooping-cough-kent-county-urging-residents-get-vaccinated/. Accessed September 15, 2018.
• Beahm A. ADPH investigating whooping cough outbreak in Jefferson, Shelby counties. Al.com website. al.com/news/birmingham/index.ssf/2018/08/adph_investigating_whooping_co.html. Updated August 4, 2018. Accessed September 15, 2018.
• Boone R. Whooping cough outbreak worsens in southwestern Idaho. US News & World Report. August 14, 2018. usnews.com/news/best-states/idaho/articles/2018-08-14/whooping-cough-outbreak-worsens-in-southwestern-idaho. Accessed September 15, 2018.
• LaCasse A. Whooping cough outbreak at Exeter High with 22 cases. Seacoastonline.com website. seacoastonline.com/news/20180618/whooping-cough-outbreak-at-exeter-high-with-22-cases. Published June 18, 2018. Accessed September 15, 2018.
• Shilhavy B. Whooping cough outbreaks continue nationwide due to failed pertussis vaccine. Health Impact News website. healthimpactnews.com/2018/whooping-cough-outbreaks-continue-nationwide-due-to-failed-pertussis-vaccine/. Accessed December 28, 2018.
• About pertussis outbreaks. CDC website. cdc.gov/pertussis/outbreaks/about.html. Updated August 7, 2017. Accessed September 15, 2018.
• Barnby E, Reynolds M. Pertussis resurgence: school nurses as a safety net for children. NASN Sch Nurse. 2018;33(5):272-278. doi: 10.1177/1942602X18767955.
• Martinón-Torres F, Heininger U, Thomson A, Wirsing von König CH. Controlling pertussis: how can we do it? A focus on immunization. Expert Rev Vaccines. 2018;17(4):289-297. doi: 10.1080/14760584.2018.1445530.
• CDC’s National Center for Immunization and Respiratory Diseases. Epidemiology and prevention of vaccine-preventable diseases. 2015 VPD Surveillance Manual, 5th ed. 2011
• CDC. Notes from the field: use of tetanus, diphtheria, and pertussis vaccine (Tdap) in an emergency department - Arizona, 2009-2010. MMWR Morb Mortal Wkly Rep. 2012;61(3):55-56.
• Winter K, Harriman K, Zipprich J, et al. California pertussis epidemic, 2010. J Pediatr. 2012;161(6):1091-1096. doi: 10.1016/j.jpeds.2012.05.041.
• CDC. Pertussis epidemic—Washington, 2012. MMWR Morb Mortal Wkly Rep. 2012;61(28):517-522.
• Walsh PF, Kimmel L, Feola M, et al. Prevalence of Bordetella pertussis and Bordetella parapertussis in infants presenting to the emergency department with bronchiolitis. J Emerg Med. 2011;40(3):256-261. doi: 10.1016/j.jemermed.2008.04.048.
• Dajani NA, Scheifele D. How long can we expect pertussis protection to last after the adolescent booster dose of tetanus-diphtheria-pertussis (Tdap) vaccines? Paediatr Child Health. 2007;12(10):873-874.
• Woo TM. Postexposure management of vaccine-preventable diseases. J Pediatr Health Care. 2016;30(2):173-184. doi: 10.1016/j.pedhc.2015.