Reduced Incidence of Infections in Very Young Children Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Background Opportunistic infections significantly contribute to morbidity and mortality after HSCT.  We hypothesized that there is a difference in the infection rate based on age at HSCT. 

Methods We retrospectively examined the medical records of 307 pediatric allogeneic HSCT recipients between 2008 and 2012 at our institution to include all positive infectious results (bacterial, viral and fungal).  Screening practices were consistent during the time period.

Results

Patients were divided into age groups: 0-2yrs (n=79), 2-5yrs (n=58) and >5yrs (n=170).  Table 1 shows the number and type of infection per group.  Viral infections differed significantly between the 0-2,  2-5 and >5 year age groups (0.72, 1.28, 1.34, respectively)  (Table 2).  The incidence of adenovirus and BK virus was lower amongst those aged 0-2 years (0.15 and 0.03) compared to those aged 2-5 years (0.38 and 0.1) and those aged >5 years (0.25 and 0.33) respectively.

There was no difference in the rates of bacteremia or fungal infections. 

Conclusion

We demonstrate there is a significantly lower rate of viral infections in children <2yrs of age undergoing allogeneic HSCT.  It is surprising to note the reduced incidence of adenovirus in children <2 years, though the difference in BK virus may be explained by the natural history of acquisition of the virus.  The overall difference may be related to their younger age at HSCT and low infectious burden compared to other age groups.  Careful monitoring and prophylaxis for high risk individuals is necessary to further reduce morbidity and mortality associated with infections in this fragile population.

Table 1.  Total number of infections per age group

Age (years)	0-2	2-5	>5
	n=78	n=58	n=170	p-value
GPC	16	18	44	0.38
GNR	21	7	31	0.09
Mold	1	0	5	0.54
Yeast	3	4	11	0.72
Viral	42	43	126	0.006
Adeno	12	21	37	0.02
BK	2	6	52	<0.0001
CMV	10	13	42	0.1
EBV	20	19	53	0.61
HHV6	4	7	11	0.25
Respiratory	16	9	41	0.38
Flu	4	0	6	0.27
Metapneumo	4	2	6	0.86
RSV	5	5	18	0.59
Paraflu	2	4	10	0.47
Rhino	6	4	11	0.95
Noro	7	5	13	0.88
Parvo	0	0	7	0.07
Rota	2	0	3	0.59
Other	0	0	1	1

GPC- gram positive cocci, GNR- gram negative rod, UTI- urinary tract infection, CMV- cytomegalovirus, EBV- Epstein-Barr virus, HHV6- human herpes virus 6, Flu- Influenza A or B, RSV- respiratory syncytial virus

Table 2.  Mean number of infections per patient.

Age	0-2	2-5	>5
	n=79	n=58	n=170	p-value
GPC	0.37	0.59	0.36	0.27
GNR	0.35	0.12	0.3	0.23
Viral	0.72	1.28	1.34	0.0002
Adeno	0.15	0.38	0.25	0.03
BK	0.03	0.1	0.33	<0.0001
CMV	0.17	0.33	0.39	0.08
EBV	0.4	0.41	0.43	0.96
HHV6	0.06	0.14	0.07	0.3
Flu	0.06	0	0.04	0.19
Metapneumo	0.04	0.03	0.05	0.81
Noro	0.09	0.1	0.08	0.9
Paraflu	0.03	0.07	0.06	0.46
Parvo	0	0	0.05	0.06
Rhino	0.1	0.07	0.07	0.71
Rota	0.03	0	0.02	0.5
RSV	0.06	0.1	0.12	0.5
Other	0	0	0.01	0.67

GPC- gram positive cocci, GNR- gram negative rod, UTI- urinary tract infection, CMV- cytomegalovirus, EBV- Epstein-Barr virus, HHV6- human herpes virus 6, Flu- Influenza A or B, RSV- respiratory syncytial virus