- Email: [email protected]
Immunisation of preterm infants
Mini-symposium
Immunisation
Immunisation of preterm infants
C. Pullan Preterm babies are a group particularly vulnerable to infection and the consequences of infection. Immunisation is probably the most clearly established preventive measure in health. Despite this, there has been a lack of clear recommendations about immunisation of preterm infants and there has been wide disparity in practice. Some have suggested delaying the start of immunisation until the baby reaches the appropriate age post expected date of delivery (EDD), some use the actual date of delivery and some an arbitrary age in between.‘*2,3 Half doses have been used.4 Suggested contraindications or special considerations, particularly to pertussis, have been numerous, many of which are likely to apply to preterm infants; some have been written down such as cerebral irritation or damage, or developmental delay5 and some have uncertain origins such as prematurity and low weight. Yet of the illnesses against which we immunise in infancy, pertussis must be the one most likely to occur and cause problems in preterm infants who may have compromised respiratory and neurological function. A baby surviving the difficulties of prematurity and then succumbing to whooping cough is a preventable tragedy.
infant, but these appear to mature in the preterm as quickly as in the term infant. Immunoglobulin levels in preterm infants are low, but this is because of low levels of passive immunity from the mother. Response to antigenic stimulation in the newborn preterm infant compared with the term infant is not significantly different; response is related to exposure to antigen rather than to gestation, Cell-mediated immune responses can be demonstrated early in gestation and these responses are also likely to be related to exposure to antigen rather than gestation. Studies in preterm infants
Timing of immunisations Theoretical background
It may be been assumed that immature babies have comparatively immature immune systems. However the evidence suggests that this is largely not SO.~ Much of the development of the immune system occurs in the 1st and 2nd trimester of pregnancy. There are deficiencies in the immunity of the newborn Connie Pullan, Consultant Community Paediatrician, Development Centre c/o City Hospital, Hucknall Nottingham NG5 1PB. Correspondence and requests for offprints to CP. Currem Pmdiarrics (1993) 3, M-191 0 1993 Longman Group UK Ltd
Child Road,
190
Responses to oral polio virus at 2 and 4 months of age in babies born at 35 weeks gestation or less7 and to diphtheria, pertussis and tetanus (DTP) starting at 2 months of age in babies of around 31 weeks gestation* have been shown to be satisfactory. A study on 51 infants born between 26 and 36 weeks satisfactory immune gestation also showed responses;g 19 of the babies were between 28 and 31 weeks gestation and 9 either 26 or 27 weeks gestation. The babies received DTP and polio starting at 3 months of age or as soon after that as possible and were tested 2-3 months after the 3rd dose at about a year of age. All received the first dose before they were 3 months post EDD. The current recommended schedule in the UK starts immunisations at the age of 2 months and has the 3rd dose of the primary course at 4 months. Studies on this schedule, including Haemophilus Influenzae type B (Hib), and looking at preterm infants are being carried out, and it will be important to take results from these studies into account. Preliminary results suggest that satisfactory immune responses are obtained in preterm infants with the current UK schedule; the durability of these responses needs to be determined.”
IMMUNISATION
OF PRETERM
INFANTS
191
Pertussisimmunisation
Recommendations
There is no evidence that prematurity poses any greater risk from side effects of pertussis vaccine. The Department of Health now recommends that preterm infants receive all immunisations as a matter of priority and there are no specific contraindications to pertussis immunisation. l1 A stable neurological condition is not a contraindication, but if there is evidence of an evolving neurological problem it is suggested that immunisation against pertussis is postponed rather than omitted. This may be because pertussis immunisation may be blamed for causing the neurological problem. In preterm infants at the age of 2 months there may well be uncertainties about the neurological status. If there are concerns about the baby, this will need careful discussion with the parents; the risks of leaving the baby unprotected against pertussis must be carefully balanced against the reasons for postponing the immunisation. If the baby is thought to be at risk of having fits, an immunisation may trigger a fit, but so will pertussis illness. If there are concerns about giving pertussis immunisation then all DTP antigens should probably be deferred rather than leaving out pertussis; single antigen pertussis has been discontinued. It would seem inappropriate to give diphtheria and tetanus alone, since the main risk for the baby at that time is pertussis; by postponing only pertussis, it is likely that pertussis will never be given. Hib and polio immunisations could be given separately.
The Department of Health Guidelines ‘Immunisation against infectious disease’ 1992,‘i states that prematurity is not a reason to postpone immunisations. The American Academy of Pediatrics Red Book” states that pretenn infants should start their immunisations at the appropriate chronological age. The following more detailed guidelines are suggested: 1. All preterm babies should be considered for a full course of immunisations including (especially) pertussis. 2. Immunisations should start at 2 months of age, regardless of the degree of prematurity, if the child is well. 3. Oral polio should be delayed until the child is about to leave the neonatal unit because of the small risk of transfer of vaccine virus. 4. If the child is thought to be at high risk of developing a neurological problem this will need careful discussion with the parents. The risks of pertussis illness need to be carefully weighed against any possible risks of pertussis vaccine. 5. Staff on the neonatal unit should discuss and encourage immunisations and check at follow up that these have been done. Parents are likely to go back to them for advice.
Responsibilitiesof neonatalunits The parents of preterm babies, particularly those who spend long periods in the neonatal unit, develop very close relationships with the staff on the unit. These medical and nursing staff will be the people to whom the parents go to for advice and in whom they have the greatest confidence. They are therefore in the best position to provide clear advice to the parent on immunisation. If the baby is still in hospital at the time immunisations should start, then they should be started in the unit. There is a small risk of transfer of polio vaccine virus from one baby to another, so it may be wise to delay polio immunisation until just prior to discharge. Clear and timely information should be relayed to the primary health care team about which immunisations have been given and when; parent held records will help this. For babies leaving the unit before the age of 2 months, a decision about timing of immunisation and the inclusion of pertussis should be made by the neonatal unit staff and this advice relayed to the parents and primary health care team.
References 1. Vohr BR, and Williams 0. Age of Diphtheria, Tetanus, and Pertussis Immunization of Special Care Nursery Graduates. Pediatrics 1986; 77: 5699.571. 2. Lingham S, Miller C, Pateman J, et al. Imrnunisation of Preterm Infants. British Medical Journal 1986; 292: 1183-5. 3. Wariya U, Richmond S, Morrell P. Innnunisation state of children born before term in the Northern region, British Medical Journal 1989; 299: 1013-1014. 4. Bernbaum J, Daft A, Samuelson J, et al. Half-Dose Immunization for Diphtheria, Tetanus, Pertussis: Response of Pretenn Infants. Pediatrics 1989; 83: 471-476. 5. Joint Committee on Vaccination and Innnunisation, Immunisation against infectious disease. London: DHSS, 1984. 6. Bernbaum J, Anolik R, Polin R, et al. Development of the Premature Infant’s Host Defense System and Its Relationship to Routine Immunizations. Clinics in Perinatology 1984; 11: 73-84. 7. Smolen P, Bland R, Heiligenstein E, et al. Antibody response to oral polio vaccine in premature infants. The Journal of Pediatrics 1983; 103: 917-919. 8. Bembaum J, Daft A, Anolik R, et al. Response of preterm infants to diphtheria-tetanus- pertussis immunizations. The Journal of Pediatrics 1985; 107: 184-188. 9. Pullan C, Hull D. Routine immunisation of preterm infants. Archives of Disease in Childhood 1989; 64: 143881441. 10. Booy R. Personal communication. 11. Joint Committee on Vaccination and Immunisation. Immunisation against Infectious Disease. London HMSO, 1992. 12. Report of the Committee of Infectious Diseases. The 1986 red book. 20th ed. Elk Grove Village: American Academy of Pediatrics, 1986.
Immunisation
Immunisation of preterm infants
C. Pullan Preterm babies are a group particularly vulnerable to infection and the consequences of infection. Immunisation is probably the most clearly established preventive measure in health. Despite this, there has been a lack of clear recommendations about immunisation of preterm infants and there has been wide disparity in practice. Some have suggested delaying the start of immunisation until the baby reaches the appropriate age post expected date of delivery (EDD), some use the actual date of delivery and some an arbitrary age in between.‘*2,3 Half doses have been used.4 Suggested contraindications or special considerations, particularly to pertussis, have been numerous, many of which are likely to apply to preterm infants; some have been written down such as cerebral irritation or damage, or developmental delay5 and some have uncertain origins such as prematurity and low weight. Yet of the illnesses against which we immunise in infancy, pertussis must be the one most likely to occur and cause problems in preterm infants who may have compromised respiratory and neurological function. A baby surviving the difficulties of prematurity and then succumbing to whooping cough is a preventable tragedy.
infant, but these appear to mature in the preterm as quickly as in the term infant. Immunoglobulin levels in preterm infants are low, but this is because of low levels of passive immunity from the mother. Response to antigenic stimulation in the newborn preterm infant compared with the term infant is not significantly different; response is related to exposure to antigen rather than to gestation, Cell-mediated immune responses can be demonstrated early in gestation and these responses are also likely to be related to exposure to antigen rather than gestation. Studies in preterm infants
Timing of immunisations Theoretical background
It may be been assumed that immature babies have comparatively immature immune systems. However the evidence suggests that this is largely not SO.~ Much of the development of the immune system occurs in the 1st and 2nd trimester of pregnancy. There are deficiencies in the immunity of the newborn Connie Pullan, Consultant Community Paediatrician, Development Centre c/o City Hospital, Hucknall Nottingham NG5 1PB. Correspondence and requests for offprints to CP. Currem Pmdiarrics (1993) 3, M-191 0 1993 Longman Group UK Ltd
Child Road,
190
Responses to oral polio virus at 2 and 4 months of age in babies born at 35 weeks gestation or less7 and to diphtheria, pertussis and tetanus (DTP) starting at 2 months of age in babies of around 31 weeks gestation* have been shown to be satisfactory. A study on 51 infants born between 26 and 36 weeks satisfactory immune gestation also showed responses;g 19 of the babies were between 28 and 31 weeks gestation and 9 either 26 or 27 weeks gestation. The babies received DTP and polio starting at 3 months of age or as soon after that as possible and were tested 2-3 months after the 3rd dose at about a year of age. All received the first dose before they were 3 months post EDD. The current recommended schedule in the UK starts immunisations at the age of 2 months and has the 3rd dose of the primary course at 4 months. Studies on this schedule, including Haemophilus Influenzae type B (Hib), and looking at preterm infants are being carried out, and it will be important to take results from these studies into account. Preliminary results suggest that satisfactory immune responses are obtained in preterm infants with the current UK schedule; the durability of these responses needs to be determined.”
IMMUNISATION
OF PRETERM
INFANTS
191
Pertussisimmunisation
Recommendations
There is no evidence that prematurity poses any greater risk from side effects of pertussis vaccine. The Department of Health now recommends that preterm infants receive all immunisations as a matter of priority and there are no specific contraindications to pertussis immunisation. l1 A stable neurological condition is not a contraindication, but if there is evidence of an evolving neurological problem it is suggested that immunisation against pertussis is postponed rather than omitted. This may be because pertussis immunisation may be blamed for causing the neurological problem. In preterm infants at the age of 2 months there may well be uncertainties about the neurological status. If there are concerns about the baby, this will need careful discussion with the parents; the risks of leaving the baby unprotected against pertussis must be carefully balanced against the reasons for postponing the immunisation. If the baby is thought to be at risk of having fits, an immunisation may trigger a fit, but so will pertussis illness. If there are concerns about giving pertussis immunisation then all DTP antigens should probably be deferred rather than leaving out pertussis; single antigen pertussis has been discontinued. It would seem inappropriate to give diphtheria and tetanus alone, since the main risk for the baby at that time is pertussis; by postponing only pertussis, it is likely that pertussis will never be given. Hib and polio immunisations could be given separately.
The Department of Health Guidelines ‘Immunisation against infectious disease’ 1992,‘i states that prematurity is not a reason to postpone immunisations. The American Academy of Pediatrics Red Book” states that pretenn infants should start their immunisations at the appropriate chronological age. The following more detailed guidelines are suggested: 1. All preterm babies should be considered for a full course of immunisations including (especially) pertussis. 2. Immunisations should start at 2 months of age, regardless of the degree of prematurity, if the child is well. 3. Oral polio should be delayed until the child is about to leave the neonatal unit because of the small risk of transfer of vaccine virus. 4. If the child is thought to be at high risk of developing a neurological problem this will need careful discussion with the parents. The risks of pertussis illness need to be carefully weighed against any possible risks of pertussis vaccine. 5. Staff on the neonatal unit should discuss and encourage immunisations and check at follow up that these have been done. Parents are likely to go back to them for advice.
Responsibilitiesof neonatalunits The parents of preterm babies, particularly those who spend long periods in the neonatal unit, develop very close relationships with the staff on the unit. These medical and nursing staff will be the people to whom the parents go to for advice and in whom they have the greatest confidence. They are therefore in the best position to provide clear advice to the parent on immunisation. If the baby is still in hospital at the time immunisations should start, then they should be started in the unit. There is a small risk of transfer of polio vaccine virus from one baby to another, so it may be wise to delay polio immunisation until just prior to discharge. Clear and timely information should be relayed to the primary health care team about which immunisations have been given and when; parent held records will help this. For babies leaving the unit before the age of 2 months, a decision about timing of immunisation and the inclusion of pertussis should be made by the neonatal unit staff and this advice relayed to the parents and primary health care team.
References 1. Vohr BR, and Williams 0. Age of Diphtheria, Tetanus, and Pertussis Immunization of Special Care Nursery Graduates. Pediatrics 1986; 77: 5699.571. 2. Lingham S, Miller C, Pateman J, et al. Imrnunisation of Preterm Infants. British Medical Journal 1986; 292: 1183-5. 3. Wariya U, Richmond S, Morrell P. Innnunisation state of children born before term in the Northern region, British Medical Journal 1989; 299: 1013-1014. 4. Bernbaum J, Daft A, Samuelson J, et al. Half-Dose Immunization for Diphtheria, Tetanus, Pertussis: Response of Pretenn Infants. Pediatrics 1989; 83: 471-476. 5. Joint Committee on Vaccination and Innnunisation, Immunisation against infectious disease. London: DHSS, 1984. 6. Bernbaum J, Anolik R, Polin R, et al. Development of the Premature Infant’s Host Defense System and Its Relationship to Routine Immunizations. Clinics in Perinatology 1984; 11: 73-84. 7. Smolen P, Bland R, Heiligenstein E, et al. Antibody response to oral polio vaccine in premature infants. The Journal of Pediatrics 1983; 103: 917-919. 8. Bembaum J, Daft A, Anolik R, et al. Response of preterm infants to diphtheria-tetanus- pertussis immunizations. The Journal of Pediatrics 1985; 107: 184-188. 9. Pullan C, Hull D. Routine immunisation of preterm infants. Archives of Disease in Childhood 1989; 64: 143881441. 10. Booy R. Personal communication. 11. Joint Committee on Vaccination and Immunisation. Immunisation against Infectious Disease. London HMSO, 1992. 12. Report of the Committee of Infectious Diseases. The 1986 red book. 20th ed. Elk Grove Village: American Academy of Pediatrics, 1986.