Pertussis infection in infants and children: Treatment and prevention

INTRODUCTION — The treatment and prevention of pertussis (whooping cough) infection in infants and children will be discussed here. The clinical presentation, including complications, and the diagnosis of pertussis in infants and children; the microbiology, epidemiology, and pathogenesis of pertussis infection; and the clinical features, treatment, and prevention of pertussis in adolescents and adults are discussed separately:

●(See "Pertussis infection in infants and children: Clinical features and diagnosis".)

●(See "Pertussis infection: Epidemiology, microbiology, and pathogenesis".)

●(See "Pertussis infection in adolescents and adults: Clinical manifestations and diagnosis".)

●(See "Pertussis infection in adolescents and adults: Treatment and prevention".)

CLINICAL COURSE — Pertussis infection often results in a protracted illness. Frequent coughing paroxysms interfere with daily function. Young infants can develop serious complications, including poor weight gain, apnea, pneumonia, respiratory failure, seizures, and death. Without antimicrobial therapy, the child is contagious throughout much of the protracted illness. (See "Pertussis infection in infants and children: Clinical features and diagnosis".)

MANAGEMENT — The management recommendations below are generally consistent with those of the United States Centers for Disease Control and Prevention [1] and the American Academy of Pediatrics [2].

Hospitalization

Indications — Indications for hospitalization in infants and children with pertussis infection or suspected pertussis infection include [3-5]:

●Respiratory distress, manifested by tachypnea, retractions, nasal flaring, grunting, and the use of accessory muscles

●Evidence of pneumonia (see "Community-acquired pneumonia in children: Clinical features and diagnosis")

●Inability to feed

●Cyanosis or apnea, with or without coughing

●Seizures

●Age <4 months (see 'Special population: Infants <4 months' below)

Isolation — Standard precautions, as well as droplet precautions (mask within 3 feet), are recommended for children with pertussis who are admitted to the hospital [2]. These precautions should be in effect until five days of effective therapy have been administered or 21 days after the onset of symptoms in untreated patients. (See "Infection prevention: Precautions for preventing transmission of infection", section on 'Droplet precautions'.)

Contact precautions are not necessary for B. pertussis but may be indicated for other conditions in the differential diagnosis until a diagnosis is confirmed (eg, respiratory syncytial virus, adenovirus, parainfluenza virus). (See "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Differential diagnosis' and "Infection prevention: Precautions for preventing transmission of infection", section on 'Contact precautions'.)

Discharge criteria — Minimum criteria for discharge include:

●Ability to tolerate coughing episodes without becoming hypoxic and/or bradycardic; most infants who are admitted to the hospital with pertussis continue to have coughing paroxysms after discharge

●Ability to eat enough to gain weight

●Reliable caretakers who are comfortable caring for the child at home

●Assurance of close outpatient follow-up

Supportive care — Supportive care is the mainstay of management for Bordetella pertussis infection.

Fluids and nutrition — Infants and children with frequent paroxysms of cough may have increased fluid and energy needs, which can be difficult to meet if the infant is coughing or vomiting. The child's fluid and nutritional status should be monitored closely, whether the child is admitted to the hospital or cared for at home.

Intravenous hydration and nasogastric feeding may be required for some hospitalized patients. The nasogastric tube may stimulate the cough reflex in some infants; however, nasogastric feedings should be attempted before parenteral nutrition for infants who are unable to gain weight because of severe coughing paroxysms.

Management of cough — The paroxysmal cough of pertussis may be severe and protracted; it is the main cause of morbidity from pertussis. Known triggers for coughing paroxysms (eg, exercise, cold temperatures, nasopharyngeal [NP] suctioning) should be avoided if possible – although NP suctioning may be necessary for diagnosis. (See "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Laboratory confirmation'.)

We do not suggest symptomatic therapies for pertussis-related cough. In small trials and a systematic review, symptomatic treatments, including bronchodilators, corticosteroids, antihistamines, and antitussive agents, have not been proven to be beneficial in patients with pertussis [6-10]. In general, the risks of these therapies outweigh the benefits, particularly for opioid cough suppressants, which may adversely affect respiration. However, based on anecdotal experience, some clinicians may attempt a trial of inhaled beta-agonists for infants with compromised respiratory status. Although pertussis-associated cough did not improve in two small trials (total of 34 patients) [7,8], increased risks of beta-agonists in patients with pertussis have not been reported.

Antimicrobial therapy

Indications — When administered early in the course (ie, within seven days of symptom onset), antimicrobial therapy for pertussis may shorten the duration of symptoms and decrease transmission to susceptible contacts [11,12]. Treatment is particularly important for infants <6 months because they are at increased risk for complications. In addition, if not treated, they remain culture positive for longer periods than do older children and adults [13-15].

●We recommend antimicrobial treatment for individuals who have B. pertussis isolated from pertussis cultures or positive polymerase chain reaction (PCR) within three weeks of cough onset (individuals >1 year) or six weeks of cough onset (individuals <1 year) [1,16].

●We also recommend treatment for infants and children with a clinical diagnosis of pertussis (with or without laboratory confirmation) who have had symptoms <21 days. (See "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Clinical diagnosis'.)

Antimicrobial therapy should be initiated based upon clinical suspicion and not on laboratory confirmation, because laboratory confirmation may take up to one week, depending on the laboratory facilities and testing methods that are available. (See "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Laboratory confirmation'.)

●Antimicrobial therapy also may be indicated for patients who have had >21 days of symptoms, particularly those who are likely to be in contact with high-risk individuals [17,18], although the utility of therapy in such patients is less clear than for patients with <21 days of symptoms.

Early treatment (ie, within seven days of symptom onset) may decrease the severity of symptoms [19]. However, most patients do not come to medical attention until the paroxysmal phase, which occurs one to two weeks after illness onset. Clinical trials and observational studies of treatment during the paroxysmal stage have yielded inconsistent results regarding the ability of treatment to alter the clinical course [20-23]. A systematic review of randomized and quasi-randomized trials of antibiotics for the treatment of pertussis concluded that antibiotic treatment does not alter the clinical course [12]. However, in many of the studies that were included, treatment was initiated after the paroxysmal phase.

Patients are most contagious during the catarrhal stage and through the first three weeks after onset of coughing spells or until five days after initiation of appropriate treatment [2]. A systematic review of randomized and quasi-randomized trials of antibiotics concluded that antibiotic treatment is effective in eradicating pertussis from the nasopharynx, thereby reducing the risk of transmission [12].

Choice of regimen — The macrolide antibiotics, erythromycin, azithromycin, and clarithromycin are the preferred antimicrobial therapies for the treatment of pertussis [1,2,24]. Macrolide-resistant B. pertussis is rare but has been reported in China [25-27], Iran [28,29], and France [30]. The preferred regimen varies with age (table 1) [1,21].

●Infants younger than one month – Azithromycin is the recommended macrolide antibiotic for the treatment of pertussis in infants younger than one month of age. It is preferred over erythromycin; clarithromycin is not recommended.

Both azithromycin and erythromycin are associated with increased risk of infantile hypertrophic pyloric stenosis (IHPS), particularly in infants younger than two weeks [31-36]. The risk of IHPS with clarithromycin is not known [37]. IHPS should be considered in young infants who develop vomiting within one month of therapy with a macrolide antibiotic given in the first month of life. Cases of pyloric stenosis associated with oral macrolide antibiotics should be reported to the US Food and Drug Administration (FDA) Safety Information and Adverse Event Reporting Program. (See "Infantile hypertrophic pyloric stenosis", section on 'Clinical manifestations'.)

●Infants and children older than one month – Any of the macrolide antibiotics (table 1) can be used for the treatment of pertussis in infants and children older than one month of age. Neither azithromycin nor clarithromycin is licensed by the FDA for use in infants younger than six months; however, azithromycin is commonly employed for pertussis treatment and prophylaxis in young infants.

Azithromycin and clarithromycin have a more convenient dosing schedule than erythromycin and are better tolerated [38,39]. Azithromycin and clarithromycin have excellent in vitro activity and have been evaluated in several clinical trials [39-42]. In the largest trial, 477 children with confirmed or suspected pertussis were randomly assigned to treatment with erythromycin or azithromycin [39]. Pertussis was eradicated from the nasopharynx of children who had positive cultures (24 percent of the total), regardless of which antibiotic they received. However, 90 percent of children who took azithromycin completed therapy, compared with 55 percent who took erythromycin.

Trimethoprim-sulfamethoxazole (TMP-SMX) is an alternative for children older than two months who have a contraindication to or cannot tolerate macrolide agents or are infected with a strain that is macrolide resistant [2]. TMP-SMX should not be used in infants younger than two months of age because of the potential risk of kernicterus related to bilirubin displacement.

Beta-lactam antibiotics (ampicillin, amoxicillin, cephalosporins) have variable activity against B. pertussis and are not recommended. Ampicillin and amoxicillin do not eradicate B. pertussis from the nasopharynx [43]. Neither tetracycline nor fluoroquinolone antibiotics are recommended for use in young children because of potential adverse effects. (See "Tetracyclines", section on 'Adverse reactions' and "Fluoroquinolones", section on 'Children'.)

Duration of therapy — The duration of therapy depends upon the agent (table 1). We suggest 5 days for azithromycin, 14 days for erythromycin, 7 days for clarithromycin, and 14 days for trimethoprim-sulfamethoxazole.

A meta-analysis evaluated randomized and quasi-randomized controlled trials of antibiotics for the treatment of pertussis that compared short-term (azithromycin for three days, clarithromycin for seven days, or erythromycin estolate for seven days) and long-term macrolide therapy (erythromycin estolate or erythromycin for 14 days) for the eradication of B. pertussis from the nasopharynx [12]. The report concluded that short-term therapy was as effective and associated with significantly fewer side effects. However, we continue to suggest a 14-day course of erythromycin, because relapses have been reported after courses of 7 to 10 days [44]. We also continue to suggest a five-day course of azithromycin, because the number of subjects treated with the shorter duration of azithromycin in the meta-analysis was small (<20 subjects) [12].

Special population: Infants <4 months — The recommendations in this section are consistent with guidance provided by the California Department of Public Health (DPH) and several California pediatric infectious disease experts based upon their experience with severe pertussis in young infants during the 2010 and 2014 outbreaks [5,45].

Treatment setting — Age <4 months is an indication for hospitalization in infants with pertussis or suspected pertussis infection given the concerns for rapid deterioration. Infants younger than four months are at increased risk for severe or fatal pertussis infection [45-47]. In a review of 53 fatal cases of pertussis in infants younger than four months from a single state (1998 to 2014), the case fatality rate was 1.2 percent; 47 of the infants were younger than two months at the time of illness onset [48].

The preadmission evaluation of infants <4 months with suspected pertussis typically includes a complete blood count with differential. It is discussed separately. (See "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Diagnosis'.)

Hospitalization at a medical center with a pediatric intensive care unit is suggested for infants younger than four months of age and white blood cell (WBC) count >30,000 cell/microL (which is associated with significant morbidity [45,48-50]) [5]. The severity of illness in young infants is unpredictable; clinical decline may occur rapidly and without warning [51]. Intensive care may be required for the management of apnea, seizures, respiratory failure, pulmonary hypertension, and/or cardiac failure. If the admitting hospital cannot provide intensive care, transfer to a hospital with an intensive care unit may be warranted [5]. (See 'Critically ill infants' below.)

Antimicrobial therapy — Antimicrobial therapy for pertussis in infants <4 months of age should be initiated immediately upon suspicion of pertussis (table 1) [5,45]. Laboratory confirmation should not delay the initiation of treatment. (See "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Infants <4 months' and 'Antimicrobial therapy' above.)

Monitoring — The respiratory rate, heart rate, oxygen saturation, and WBC count of infants who are admitted to the hospital for pertussis (suspected or confirmed) should be monitored. For infants younger than four months, some experts [45] suggest continuous cardiorespiratory monitoring and WBC count every 12 hours with transfer to the pediatric intensive care unit if the WBC count increased by ≥50 percent in 24 hours [45]. For infants ≤60 days of age, they also suggest chest radiography to evaluate pneumonia and echocardiography to evaluate pulmonary hypertension.

Case series suggest that exchange transfusion or leukapheresis may be helpful in the management of pertussis-related respiratory failure, pulmonary hypertension, and cardiac failure [52-57], but it must be performed before the infant is in severe distress or has multiorgan failure [48,56]. (See 'Critically ill infants' below.)

Documentation of oral intake and the severity of coughing spells (eg, whether they are associated with hypoxia or bradycardia) and apneic episodes are helpful in discharge planning. The frequency of coughing spells and apnea decrease before severity; thus, discharge decisions should be based upon the severity of coughing spells and apnea rather than the frequency [5]. (See 'Discharge criteria' above.)

Critically ill infants — Critically ill infants include those with apnea, seizures, or pneumonia complicated by respiratory failure, pulmonary hypertension, and/or cardiac failure. Complicated pneumonia usually occurs in association with WBC count ≥30,000 cells/microL [48].

A full discussion of the intensive care management of infants with pertussis is beyond the scope of this review. Guidelines for the intensive care unit management of infants with pertussis are provided by the California DPH, and summarized below. Management or consultation with an intensivist may be most appropriate in these instances.

●Apnea – Infants with significant apnea (eg, if adequate ventilation is a concern) may require mechanical ventilation.

●Seizures – Seizures in infants with pertussis are treated in the same manner as seizures due to other causes. (See "Seizures and epilepsy in children: Initial treatment and monitoring".)

●Pneumonia complicated by refractory hypoxemia, pulmonary hypertension, and/or cardiac failure – This scenario is typically associated with extreme leukocytosis and has a mortality of up to 80 percent [47,48,57,58]. In young infants with pertussis, WBC count ≥30,000 cells/microL has been associated with increased severity and death.

Based on the California outbreak experience, some infectious disease experts suggest exchange transfusion for infants with pertussis who are younger than four months and have any of the following [5,45,48,56,58]:

•WBC count ≥25,000/microL with lymphocyte count ≥12,000/microL and one or more of the following:

-Cardiogenic shock

-Pulmonary hypertension

-Organ failure (eg, renal failure)

•Total WBC ≥48,000/microL with lymphocyte count ≥15,000/microL

•Total WBC ≥30,000/microL with lymphocyte count ≥15,000/microL if the rate of rise was ≥50 percent in 24 hours

Additional indications for exchange transfusion include pulse rate consistently >170 beats/minute, respiratory rate consistently >70 breaths/minute, and oxygen saturation of <80 percent [45].

Given the potential for severe or fatal pertussis infection in young infants, the recommendations above have been generalized to all infants based upon observational data in infants <4 months of age who were admitted to an intensive care unit. In case series, hypoxemia, pulmonary hypertension, and cardiac failure that were unresponsive to other measures improved after exchange transfusion [52-56]. In a 2014 literature review of 47 reported cases of critical pertussis treated with exchange transfusion, 30 (64 percent) survived [59]. The technique for double volume exchange transfusion is the same as that used for newborns with hyperbilirubinemia [5,60]. (See "Unconjugated hyperbilirubinemia in term and late preterm newborns: Escalation of care", section on 'Exchange transfusion'.)

For infants who do not improve with exchange transfusion, extracorporeal membrane oxygenation (ECMO) may be warranted as a life-saving measure; however, in a review of 61 children with pertussis who were treated with ECMO, the mortality rate was 70.5 percent [57].

Given the sparsity of data, consultation with an experienced pediatric intensivist is suggested before undertaking exchange transfusion or ECMO for the treatment of pertussis in young infants.

PREVENTION — The prevention recommendations below are generally consistent with those of the United States Centers for Disease Control and Prevention [1] and the American Academy of Pediatrics [2].

Postexposure prophylaxis

Indications and timing — We suggest postexposure antimicrobial prophylaxis for all household and close contacts of the index case and for exposed individuals at high risk for severe or complicated pertussis, even if the exposed person is fully immunized. Postexposure prophylaxis is most effective when initiated within 21 days of the onset of cough in the index patient [1]. The utility of postexposure prophylaxis after 21 days of onset of cough in the index case is unclear.

●Close contacts – Close contacts are defined by [1]:

•Living in the same household

•Face-to-face exposure within 3 feet of a symptomatic patient

•Direct contact with respiratory, oral, or nasal secretions from a symptomatic patient

•Sharing the same confined space in close proximity with a symptomatic patient for ≥1 hour

Local public health officials should be consulted for recommendations regarding control of pertussis in schools. Prophylaxis for entire schools or classrooms usually is not recommended.

●High risk – Individuals who should receive postexposure prophylaxis because they are at high risk for severe or complicated pertussis or they may expose individuals who are at high risk include [1]:

•Infants younger than one year, particularly those younger than four months

•Pregnant women

•Persons with immunodeficiency

•Persons with underlying medical conditions (chronic lung disease, respiratory insufficiency, cystic fibrosis)

•Persons who have contact with infants

Factors to consider in decisions about postexposure prophylaxis include the contagiousness of the patient, the intensity of the exposure, the potential for consequences of severe pertussis in the contact, and the possibility for secondary exposure of persons at high risk of severe infection from the contact [1]. The benefits of prophylaxis must be weighed against the potential adverse effects. (See 'Choice of regimen' above.)

It is not necessary for asymptomatic contacts who are receiving antimicrobial prophylaxis to avoid contact with high-risk individuals [61]. Symptomatic contacts who are receiving antimicrobial prophylaxis should avoid contact with high-risk individuals until they have completed five days of antimicrobial prophylaxis.

Retrospective epidemiologic studies suggest that early chemoprophylaxis is associated with decreased risk of transmission of pertussis [62-64]. In the only randomized trial, erythromycin was 68 percent efficacious in preventing culture-confirmed pertussis in household contacts [65]. However, there was no difference in duration of respiratory symptoms between the treatment and placebo groups. Twenty percent of household contacts in both groups had symptoms consistent with pertussis before treatment was initiated. A post-hoc analysis excluding these subjects demonstrated no difference in the secondary attack rate between treatment and placebo groups, but the sample size may have been too small to detect a significant difference. Therefore, antimicrobial prophylaxis continues to be recommended for close contacts of patients with pertussis.

Regimen — The antibiotic regimens for postexposure prophylaxis are identical to those used for treatment of pertussis (table 1) [1,2,62,63].

Immunization — We recommend age-appropriate immunization against pertussis for infants, children, adolescents, and adults (figure 1A-C). Immunization against pertussis has dramatically reduced the burden of disease.

●Routine immunization – Routine immunization of infants, children, adolescents, and adults (particularly pregnant women) is the most important preventive strategy [1]. Routine vaccination against pertussis is discussed separately. (See "Diphtheria, tetanus, and pertussis immunization in children 7 through 18 years of age" and "Pertussis infection in adolescents and adults: Treatment and prevention", section on 'Vaccination' and "Immunizations during pregnancy", section on 'Tetanus, diphtheria, and pertussis vaccination' and "Diphtheria, tetanus, and pertussis immunization in children 6 weeks through 6 years of age", section on 'Indications'.)

●Immunization of contacts – Close contacts of the index case who are unimmunized or underimmunized should have pertussis immunization initiated or continued according to the recommended schedule [2]. (See "Diphtheria, tetanus, and pertussis immunization in children 7 through 18 years of age", section on 'United States' and "Diphtheria, tetanus, and pertussis immunization in children 6 weeks through 6 years of age", section on 'Schedules'.)

●Immunization after pertussis infection – Well-documented pertussis infection (eg, a positive culture for B. pertussis or an epidemiologic link to a culture-positive case) is likely to confer immunity against pertussis [66]. However, the duration of immunity is unknown, and pertussis infection can reoccur as immunity wanes. We agree with the American Academy of Pediatrics recommendation that children who have had well-documented pertussis disease complete age-appropriate immunization with an acellular pertussis-containing vaccine (either diphtheria toxoid, tetanus toxoid and acellular (DTaP) vaccine or tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis [Tdap] vaccine) [2]. (See "Diphtheria, tetanus, and pertussis immunization in children 7 through 18 years of age", section on 'United States' and "Diphtheria, tetanus, and pertussis immunization in children 6 weeks through 6 years of age", section on 'Schedules'.)

●Neonatal immunization – Early neonatal immunization is a strategy that is being studied [67-69] but is not yet recommended.

Infection control — Infection control measures for hospitalized patients are discussed above. (See 'Hospitalization' above.)

In the outpatient setting, symptomatic contacts of the index case of pertussis should avoid contact with high-risk individuals until they have completed five days of antimicrobial prophylaxis [61]. It is not necessary for asymptomatic contacts who are receiving antimicrobial prophylaxis to avoid contact with high-risk individuals.

Return to school or day care — Because of the high risk of transmission, infected children should be excluded from school or day care until they have completed five days of effective antimicrobial therapy (regardless of the antimicrobial agent), or, if they are not treated, 21 days after the onset of symptoms [2]. Contacts of an infected child should be closely observed for development of respiratory symptoms for at least 21 days after the last contact with the infected individual.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pertussis".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient education" and the keyword[s] of interest.)

●Basics topic (see "Patient education: Whooping cough (The Basics)")

●Beyond the Basics topics (see "Patient education: Vaccines for infants and children age 0 to 6 years (Beyond the Basics)" and "Patient education: Vaccines for children age 7 to 18 years (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Indications for hospitalization include increased work of breathing, pneumonia, inability to feed, cyanosis, apnea, seizures, and age <4 months (given concerns for rapid deterioration). For infants <4 months, hospitalization at a major medical center with a pediatric intensive care unit may be desirable because clinical decline may occur rapidly and without warning. (See 'Hospitalization' above and 'Special population: Infants <4 months' above.)

●Supportive care is the mainstay of treatment for pertussis in infants and children. Particular attention must be paid to the child's fluid and nutritional status. (See 'Supportive care' above.)

●Known triggers for coughing paroxysms (eg, exercise, cold temperatures, nasopharyngeal suctioning) should be avoided if possible. Symptomatic treatments including bronchodilators, corticosteroids, antihistamines, and antitussive agents have not been proven to be beneficial in improving the cough in patients with pertussis. (See 'Management of cough' above.)

●When administered early in the course, antimicrobial therapy can shorten the duration of symptoms and decrease transmission to close contacts. Early initiation of antimicrobial therapy entails a high degree of clinical suspicion, since laboratory confirmation of the diagnosis can take as long as a week. (See "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Diagnosis'.)

●Given the ability of antibiotics to eradicate pertussis from the nasopharynx, we recommend antimicrobial treatment for infants and children who have Bordetella pertussis isolated from cultures or have positive polymerase chain reaction for pertussis (Grade 1A). (See 'Indications' above and "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Diagnosis'.)

●We also recommend antimicrobial treatment for patients with a clinical diagnosis of pertussis who have had symptoms for less than 21 days (Grade 1B). (See 'Indications' above and "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Diagnosis'.)

●We recommend macrolide antibiotics for the treatment and prophylaxis of pertussis (table 1) (Grade 1A). Trimethoprim-sulfamethoxazole may be an alternative for patients who have a contraindication to or cannot tolerate macrolide agents (table 1). (See 'Choice of regimen' above.)

●Infantile hypertrophic pyloric stenosis should be considered in young infants who develop vomiting within one month of therapy with a macrolide antibiotic given in the first month of life. (See 'Choice of regimen' above and "Infantile hypertrophic pyloric stenosis".)

●We suggest antimicrobial prophylaxis for household and close contacts of the index case and for individuals at high risk for severe or complicated pertussis (Grade 2B). (See 'Postexposure prophylaxis' above.)

●The regimen for antimicrobial prophylaxis is the same as that for treatment (table 1). Antimicrobial prophylaxis should be initiated within 21 days of onset of cough in the index case. (See 'Regimen' above.)

●For incompletely immunized children with well-documented pertussis infection, we suggest completion of immunization with an acellular pertussis-containing vaccine (either diphtheria toxoid, tetanus toxoid, and acellular pertussis [DTaP] vaccine or tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis [Tdap] vaccine) rather than diphtheria toxoid and tetanus toxoid vaccine (Grade 2C). (See 'Immunization' above and "Diphtheria, tetanus, and pertussis immunization in children 6 weeks through 6 years of age" and "Diphtheria, tetanus, and pertussis immunization in children 7 through 18 years of age".)

●Children with pertussis or suspected pertussis may return to school or day care after they have completed five days of effective antimicrobial therapy or, if they are not treated, 21 days after the onset of symptoms. (See 'Return to school or day care' above.)