Article: Protect Vulnerable Infants from Pertussis

Pertussis is a continuing threat to Californians, though the magnitude of the threat varies by year as the number of susceptible people in the population waxes and wanes. Over 9,100 cases of pertussis, including 10 fatal infant cases, were reported in California during 2010 - the most in more than a half-century. Consistent with historical cycles of 3-5 years between years of higher incidence, cases are likely to increase between 2013 and 2015 in comparison to 2011 and 2012¹.

Immunize Pregnant Women with Tdap during Every Pregnancy

Infants younger than two months of age are most susceptible to hospitalization or death from pertussis, but immunization against pertussis is not recommended until at least 6 weeks of age. However, infants can be protected by maternal antibodies that are transferred through the placenta. Early evidence suggests that vaccinating pregnant women with Tdap during the third trimester of pregnancy can prevent pertussis in young infants. 

Optimal Timing of Maternal Tdap Administration

To maximize protection of young infants, the federal Advisory Committee on Immunization Practices (ACIP) recommends that all women should be administered Tdap during every pregnancy, regardless of previous Tdap status, preferably between 27 and 36 weeks’ gestation²:

• Women immunized with Tdap during a prior pregnancy or during the first or second trimester of a current pregnancy appear to have low levels of pertussis antibodies at delivery.³ 
• Transplacental transport of antibodies occurs mainly after 30 weeks’ gestation. 
• At least two weeks are needed for a maximal response to immunization.²

If Tdap is not administered during pregnancy, it should be given immediately postpartum. This will not provide direct protection to the infant, but may prevent transmission of pertussis from mother to infant.² 

Other Close Contacts of Infants

Anyone who lives or works (e.g., parents, siblings, grandparents, childcare providers, and healthcare personnel) with infants younger than 12 months of age should receive Tdap if they have not already done so.² ACIP is currently considering whether Tdap boosters are indicated for contacts of infants.

Recognize and Appropriately Treat Pertussis in Young Infants⁴

When pertussis has not been prevented and a young infant is infected, prompt diagnosis and appropriate treatment are critical.  However, many young infants with pertussis are seen by clinicians multiple times without a diagnosis of pertussis being considered.

Very young infants with pertussis may look deceptively well with a runny nose but little or no fever or cough.  The lack of fever and the mildness of initial symptoms often results in clinicians underestimating the potential severity of the illness, which leads to a delay in diagnosis and effective treatment.  

Parents may report episodes where the infant has:

• Gagged or gasped
• Stopped breathing (apnea)
• Turned blue (cyanosis), red or purple in the face
• Vomited after coughing

Pertussis in infants should be diagnosed by culture or PCR using a properly collected nasopharyngeal specimen (swab or aspirate).⁵ A high white blood cell count (leukocytosis) of  ≥20,000 cells/mm³ with ≥50% lymphocytes (lymphocytosis) in any young infant with a cough illness is a strong indication of B. pertussis infection.⁴

If pertussis is a possible diagnosis in a young infant, treatment with azithromycin should be started immediately.⁶ All young infants (3 months old or younger) with possible pertussis should be admitted to the hospital, and many will require intensive care. 

There are no clinical exam findings that help predict which infants will progress to severe, life-threatening disease; all infections in infants, particularly those 3 months old or younger, should be considered serious until observation during antimicrobial treatment suggests otherwise.

Consider Pertussis Regardless of Age or Immunization Status

Because the pertussis vaccines, DTaP or Tdap, are not completely effective, pertussis can still occur in fully immunized persons, contributing to its spread. Remain alert for the symptoms of pertussis  in infants, children or adults regardless of their immunization status, and test for pertussis when symptoms are consistent. Most pertussis infections, especially in adults, are undiagnosed.

References

1. California Department of Public Health. Pertussis summary reports. http://www.cdph.ca.gov/programs/immunize/Pages/PertussisSummaryReports.aspx 
2. CDC. Updated Recommendations for Use of Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccine in Pregnant Women-Advisory Committee on Immunization Practices, 2012. MMWR, 2013; 62 (7): 131-135. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6207a4.htm 
3. Healy CM, Rench MA, Baker CJ. Importance of timing of maternal Tdap immunization and protection of young infants. Clin Infect Dis 2013;56:539-44.
4. Cherry JD, Harrison R, Bradley JS, Weintrub P, Lehman S, Duthie S, Mason WH. Pertussis in Young Infants – Guidance for Clinicians. June 2011. Available at:
   https://www.cdph.ca.gov/HealthInfo/discond/Documents/Cherry_Pertussis%20in%20Young%20Infants2_June%202011.pdf (PDF) 
5. California Department of Public Health. Pertussis Laboratory Testing. February 2011. http://www.cdph.ca.gov/programs/immunize/Documents/PertussisLaboratoryTesting.pdf (PDF)
6. California Department of Public Health. Pertussis Public Health Investigation. June 2013.
   http://www.cdph.ca.gov/healthinfo/discond/documents/cdph_pertussis_quicksheet.pdf (PDF)