Immunization status and re-immunization of childhood acute lymphoblastic leukemia survivors

ABSTRACT

Intensive chemotherapy can cause long-lasting immunosuppression in children who survived cancer. The immunosuppression varies according to the type of cancer, intensity of chemotherapy and age of the patient. A sufficient immune reconstruction when has been completed in childhood cancer survivors, the re-vaccination program can achieve sufficient antibody levels for some of the life-threatening vaccine-preventable infectious diseases. This study evaluates the serological status of pediatric acute lymphoblastic leukemia (ALL) cases before and after the intensive chemotherapy treatment. Antibodies against measles, mumps, rubella, varicella, hepatitis A and B were tested with the enzyme-linked immunosorbent assay (ELISA) method. Antibody titers were measured firstly at the leukemia diagnosis time when the chemotherapy was not started. The second evaluation of antibody titers was studied at 6 months after the cessation of chemotherapy for all patients. Forty-six patients with the mean age of 6.1 ± 4.5 years were participated in this study. Changing to seronegative after treatment was significantly different in measles, rubella, hepatitis A and hepatitis B (p < .05). Seventy-eight (28%) antibody levels in the patients were non-protective for all diseases. Only three (7%) patients had protective antibody levels for all diseases in the sixth month of chemotherapy cessation. There was a negative correlation between patient’s age and losing protective antibody levels for any vaccine-preventable disease (p < .05). Antibody levels against vaccine-preventable diseases have evident that reduced after ALL treatment at childhood. Pediatric ALL survivors must be re-vaccinated for vaccine-preventable diseases after achieving immune reconstruction.

KEYWORDS:

• Childhood
• cancer
• immunity
• leukemia
• vaccination
• survivors

Introduction

The leukemias are the most often malignancies in children and it accounts for a third of childhood cancers. They occur abnormal proliferation of hematopoietic stem cells leading to interruption of normal healthy cell production. Acute lymphoblastic leukemia (ALL) has constituted about 75% of leukemias in children.^{1, 2} Most of pediatric ALL cases are survived due to more intensive chemotherapy, improved supportive care and better followed-up conditions.^3,4 However, intensive chemotherapy can cause long-lasting immunosuppression particularly due to depletion of T and B cells and also patients may begin to be more vulnerable to infections due to antibodies provided by vaccination to decrease or disappear.^1,5,6 The immunosuppression varies according to the type of cancer, intensity of chemotherapy and age of the patient. A sufficient immune reconstruction is generally completed in childhood cancer survivors sixth months after the treatment ending and the re-vaccination program can achieve sufficient antibody levels for some of the life-threatening vaccine-preventable infectious diseases.^7,8

This study was to evaluate the serological status of pediatric ALL cases before and after the intensive chemotherapy treatment and also research features of patients who were seronegative with vaccine-preventable diseases including measles, mumps, rubella, varicella, hepatitis A and B.

Patients and methods

This retrospective cross-sectional study was performed at a tertiary care hospital in Turkey. Throughout 2010 to 2017, data of 46 pediatric ALL survivors, whose pre- and posttreatment antibody levels were reached, were reviewed from their medical records. The demographic features of patients were enrolled (Table 1). All patients were classified to risk groups and treated with the ALL Intercontinental Berlin–Frankfurt–Münster (ALL-IC BFM) 2009 protocol. Patients who completed maintenance therapy 6 months ago were vaccinated according to the Infectious Diseases Society of America (IDSA) after serologically tested.⁸ The caregivers of patients have declared that they were vaccinated their children according to the national vaccination program. The recommended and intermittently updated national vaccination program of The Turkey Ministry of Health is shown in Table 2.

Table 1. Demographic features of patients who participated to study

Variable	Number (n)
Sex (%)  Male  Female	17 (37) 29 (63)
Age at diagnoses (year)  Mean ± SD  Median (range)	6.1 ± 4.5 4.0 (2–17)
White blood cell count (/mm^3)  Mean ± SD  Median (range)	13.600 ± 17.300 8800 (1200–85.100)
ALL risk group (%)  SRG  IRG  HRG	13 (28) 29 (63) 4 (9)
Pretreatment seronegativity (%)  Measles  Mumps  Rubella  Varicella  Hepatitis A  Hepatitis B	11 (24) 16 (35) 1 (2) 21 (46) 18 (39) 11 (24)
Postreatment seronegativity (%)  Measles  Mumps  Rubella  Varicella  Hepatitis A  Hepatitis B	27 (59) 21 (46) 11 (24) 24 (52) 38 (83) 35 (76)

SD: standard deviasion,

Table 2. The recommeded national vaccination program of The Turkey Ministry of Health

Vaccine	Time
	At born	1^st Month	2^nd Month	4^th Month	6^th Month	12^th Month	18^th Month	24^th Month	6^th Year	14^th Year
Hepatitis B	+	+			+
BCG			+
DTaP-IPV-HiB			+	+	+		+
PCV*			+	+		+
MMR						+			+
DTaP									+
OPV					+		+
Td										+
Hepatitis A**							+	+
Varicella***						+

BCG; Bacillus Calmette–Guérin vaccine

DTaP-IPV-HiB; diphteria, tetanus toxoids, acelluler pertusis – inactivated polio – haemophilus influenzae type B

PCV; pneumococcal conjugate vaccine

MMR; measles, mumps, rubella

OPV; oral polio vaccine

Td; Tetanus, (reduced) diphteria

*PCV was added to the national program in 2011.

**Hepatitis A vaccine was added to the national program in 2012.

***Varicella vaccine was added to the national program in 2013.

Antibody levels in the serum of patients against to measles, mumps, rubella, varicella, hepatitis A and B were tested using an immunological method: the Enzyme-linked Immunosorbent Assay (ELISA) which commonly used to detect antibodies in serum. The serologic status (positive or negative) of patients was evaluated according to the laboratory test manufacturer's references. Antibody titers were measured firstly at the leukemia diagnosis time when the chemotherapy was not started. The second evaluation of antibody titers was studied at 6 months after the cessation of chemotherapy for all patients. Patients with non-protective antibody titers were vaccinated with non-live vaccines before the start of intensive chemotherapy.

Collected data were analyzed using descriptive statistics; frequency, mean and standard deviation were calculated. Willcoxon test was used to changing seronegative in vaccine-prevented diseases after treatment. Mann–Whitney U test was used to compare the serological difference in patients for demographic features. One-way analysis of variance (ANOVA) test was used to analyze correlation between age and serological situation. A p-value <0.05 was considered significant.

Results

Forty-six patients (17 males, 29 females) were participated in this study. The mean age was 6.1 ± 4.5 and the median age was 4.0 years (range 2–17). Also the mean count of white blood cells (WBCs) was 13.600 ± 17.100/mm³ and the median count was 8800/mm³ (range 1200–85.100/mm³) at the diagnosis of ALL in patients. Patients were 13 (28%) in standard-risk group (SRG), 29 (63%) in the ıntermediate-risk group (IRG) and 4 (9%) in high-risk group (HRG). We determined that 24% were seronegative for measles, 35% for mumps, 2% for rubella, 46% for varicella, 39% for hepatitis A and 24% for hepatitis B at the diagnosis of ALL. Six months after the cessation of chemotherapy for each patient, antibody titers were repeated; we found that 59% were seronegative for measles, 46% for mumps, 24% for rubella, 52% for varicella, 83% for hepatitis A and 76% for hepatitis B. Changing to seronegative after treatment were significantly different in measles (p = .000), rubella (p = .002), hepatitis A (p = .000) and hepatitis B (p = .000). Therefore, no significant difference was observed in mumps (p = .059) and varicella (p = .180) (Table 3).

Table 3. Serologic features of patients at diagnosis time and end of chemotherapy

Disease	Rate of unprotectivity		After end of chemotherapy change P value
	Diagnosis time n (%)	Six months after end of chemotherapy n (%)
Measles Mumps Rubella Varicella Hepatitis A Hepatitis B	11 (24) 16 (35) 1 (2) 21 (46) 18 (39) 11 (24)	27 (59) 21 (46) 11 (24) 24 (52) 38 (83) 35 (76)	0.000 ^w 0.059 ^w 0.002 ^w 0.180 ^w 0.000 ^w 0.000 ^w

p of significance if <0.05, ^w Willcoxon test

We evaluated 276 antibody titers for six diseases (measles, mumps, rubella, varicella, hepatitis A and hepatitis B) in 46 patients before the start of chemotherapy. Seventy-eight (28%) antibody levels in the patients were non-protective for these diseases. Also, seven (15%) patients had protective antibody levels for six diseases and 27 (69%) patients had protective antibody levels for at least four diseases.

Six months after the maintenance therapy the antibody titers were reevaluated to planning re-immunization in patients. One hundred forty-three (52%) of 276 antibody levels were determined non-protective for diseases. Only three (7%) patients had protective antibody levels for six diseases and 15 (33%) patients had protective antibody levels for at least four diseases.

No statistically significant difference was observed between seronegative and seropositive patients for criteria of sex (p > .05). There was a negative correlation between patient’s age and losing protective antibody levels for any vaccine-preventable disease (p < .05). Nevertheless, there were statistically significant differences between varicella’s, hepatitis A’s protective antibody levels after cessation of chemotherapy and patient's age (<5 years vs. ≥5 years) (p < .05). Except varicella serology, there were no statistically significant differences between seronegative and seropositive patients for criteria of ALL risk group (Table 4).

Table 4. The comparison of patients’ features and serology

	Sex			Age at the diagnosis			ALL risk group
	Male (17)	Female (29)	P	<5 years (25)	≥5 years (21)	P	SRG (13)	IRG or HRG (33)	P
Measles
Seronegative Seropositive	8 9	19 10	0.225	13 12	14 7	0.320	8 5	19 14	0.808
Mumps
Seronegative Seropositive	8 9	13 14	0.885	13 12	8 13	0.351	6 7	15 18	0.966
Rubella
Seronegative Seropositive	4 13	7 20	0.963	7 18	4 17	0.483	3 10	8 25	0.934
Varicella
Seronegative Seropositive	12 5	12 17	0.058	18 7	6 15	0.004 ^m	10 3	14 19	0.037 ^m
HepatitisA
Seronegative Seropositive	15 2	22 5	0.313	17 8	20 1	0.022 ^m	12 1	25 8	0.208
HeaptitisB
Seronegative Seropositive	14 3	21 8	0.451	20 5	15 6	0.502	10 3	25 8	0.934

p of significance if <0.05, ^mMann-whitney u test

Discussion

Nowadays pediatric cancers have shown the second major cause of death in developed countries but the overall survival of pediatric cancers has been increasing over the years thanks to multidisciplinary cooperation grounded to chemotherapy, radiotherapy, surgery, hematopoietic stem cell transplantation, and of course; advanced supportive therapies.^7,9

An important part of supportive therapy is the re-immunization of pediatric cancer survivors from some of life-threatening vaccine-preventable infectious diseases. Also these patients are potentially at risk of influenza due to immunosuppression and frequent hospital visits.⁸ The chemotherapeutics cause a quantitative loss of B cells and particularly in the group of specific memory B cells leading to a reduction of specific antibodies.^3,10

We found that number of patients with protective antibody levels for each disease was decreased in the previous studies.^3,11 We determined statistically difference changing seronegative in four vaccine-prevented diseases (measles, rubella, hepatitis A and B). In the previous studies, Fayea et al.⁶ reported significant increases in non-protective antibody levels of measles, mumps, diphtheria and tetanus were monitored after chemotherapy in childhood cancer survivors and Zignol et al.¹² recommended that the non-protective antibody levels in rubella, measles, and mumps were stimulated by chemotherapy. In our study, only one patient had a non-protective antibody level for rubella before chemotherapy but 11 (24%) patients were seronegative for rubella after the cessation of chemotherapy. Some published data demonstrate protective antibody levels in rubella after treatment of ALL in childhood with wide variance of 70–92%.¹⁰ High frequency of losing protective antibody levels for any vaccine-preventable disease can be explained according to type of vaccine.⁷

Fayea et al.⁶ published that more than 90% of the patients were monitored seronegative for at least one vaccine-preventable disease and Garonzi et al.¹³ reported that 83% of patients had non-protective antibody levels for at least one vaccine-preventable disease. In our study, 93% of patients had non-protective antibody levels for at least one disease.

Similar to Fouda et al.¹⁴ report, we found that there was no significant difference between seronegative and seropositive patients for criteria of sex. Some reports found that the younger age was significantly different from losing protective antibody levels.^6,11,14 This result can be related to ineffective vaccination or uncompleted national vaccination program at younger ages.¹³ In our study and Keskin Yildirim et al.¹⁵ report, there was negative correlation between patient’s age and losing protective antibody levels for any vaccine-preventable disease. Nevertheless, there was significant difference between varicella’s, hepatitis A’s protective antibody levels after cessation of chemotherapy and patient's age.

Aytac et al.¹⁶ reported that there was a significant difference in the gender of patients and males were more seropositive for MMR. There was no significant difference in the gender of patients in Keskin Yildirim et al.¹⁵ and our study. Immune recovery was slower in high-risk group of childhood ALL than standard/intermediate-risk groups.¹⁷,¹⁸ Keskin Yildirim et al.¹⁵ found that the seronegativity of mumps was significantly higher in patients with leukemia than other cancers. Nilsson et al.³ and Fouda et al.¹⁴ reported that there was no a significant difference between ALL risk groups (standard vs. intermediate vs. high) and protective antibody levels for vaccine-preventable diseases. Also, Aytac et al.¹⁶ reported a similar result in MMR serology as Nilsson et al.³ and Fouda et al.¹⁴ reports. In our study, except varicella, there was no significant difference between ALL risk groups (standard vs. intermediate/high) and protective antibody levels. Varicella seronegativity rate was significantly more in intermediate/high-risk groups than standard-risk group.

The risk of venous thromboemboli increases in children with leukemia particularly at induction phase related to central venous catheters and exposure to corticosteroid or L-asparaginase.¹⁸ We did not detect relationship between coagulopathy and vaccination in patients during intensive chemotherapy and re-immunization period.

Conclusion

Our study results of antibody levels against vaccine-preventable diseases have evident that reduced after ALL treatment at childhood. We suggest that pediatric ALL survivors must be re-vaccinated for vaccine-preventable diseases after achieving immune reconstruction.

Disclosure of potential conflicts of interest

No potential conflicts of interest were disclosed.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the National Cancer Institute research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.