VII THE CHILDHOOD IMMUNISATION PROGRAMME IN SINGAPORE IMMUNISATION PROGRAMME IN 2002 7. 7 The childhood immunisation programme in Singapore offers vaccination against tuberculosis, hepatitis B, diphtheria, pertussis, tetanus (DPT), poliomyelitis, measles, mumps and rubella (MMR). Only diphtheria and measles immunisations are compulsory by law. Since 1 January 1990, the monovalent measles vaccine given to one-year-old children was replaced by the trivalent measles, mumps and rubella (MMR) vaccine. As of 1 Jan 1998, the monovalent rubella vaccine given to primary school leavers was replaced by the second dose of MMR vaccine (Table 7.1). Hepatitis B vaccination for infants born to carrier mothers was incorporated into the national childhood immunisation programme in October 1985. This was extended to all newborns through the use of Medisave since 1 September 1987. To protect those who were born before 1987, a 4-year hepatitis B immunization programme was implemented for students in secondary 3, junior college year 2, pre-university year 3, institutes of technical education, polytechnics and universities in January 2001. In addition, full-time national servicemen who were non-immune were offered hepatitis B immunization. The report does not cover BCG vaccination. This is prepared separately by the Communicable Disease Centre, Tan Tock Seng Hospital. IMPLEMENTATION OF THE IMMUNISATION PROGRAMME The vaccination programme was carried out by: (a) Restructured polyclinics of the National Healthcare Group (NHGP) and the Singapore Health Service (SingHealth); (b) School Health Service (SHS) of the Health Promotion Board and (c) Private medical practitioners. 7-1
Table 7.1 Recommended childhood immunisation programme, Singapore, 2002 DISEASES PRIMARY COURSE B O O S T E R D O S E S Infants (< 1 years) TUBERCULOSIS Birth - BCG without Mantoux test DIPHTHERIA* 3 months PERTUSSIS DPT (1st Dose) TETANUS 4 months DPT (2nd Dose) 5 months DPT (3rd Dose) POLIOMYELITIS* 3 months 4 months Pre-school children (1-5 years) Direct BCG if no previous vaccination 18 months DPT (1st Booster) 18 months 1st Booster Primary school students (6-12 years) 6-7 years (Primary school entrants) Direct BCG if no previous vaccination. 6-7 years (Primary school entrants) DT (2nd Booster) 11-12 years (Primary school leavers) DT (3rd Booster) 6-7 years (Primary school entrants) Either: (a) Primary course for those who have never been vaccinated; or (b) 2nd Booster for those who had been vaccinated. Secondary school students (12-15 years) 5 months MEASLES/MUMPS/ RUBELLA 1 year (1st dose) 11-12 years (Primary school leavers) 3rd Booster 11-12 years (Primary school leavers) 2 nd dose HEPATITIS B +Birth, 1, 5-6 months 4-year (2001-2004) hepatitis B immunization programme for Sec 3, JC year 2, centralized institutes year 3, ITEs, polytechnics and universities * When the recommended time schedule is not followed, then the time interval between the different doses should be adhered to. Interrupting the recommended schedule or delaying subsequent doses does not reduce the ultimate immunity. There is no need to restart a series regardless of the time elapsed between doses. However, to help ensure seroconversion, completion of the primary series of three doses is recommended. + HBIG (0.5 ml) given at the same time as the first dose of vaccine only for babies born to HBeAg (hepatitis B e antigen)-positive mothers. An additional dose of hepatitis B vaccine for babies born to HBsAg-positive mothers at 12 months. 7-2
Immunisation of pre-school children was the responsibility of the polyclinics. The target population was based on notification of births obtained from the Registrar of Births and Deaths. Follow-up home visits and telephone reminders were routinely carried out by staff nurses of the polyclinics to cover missed cases or defaulters of the programme. The SHS was responsible for the immunisation of school children. The target population was based on student population data from the Ministry of Education. NOTIFICATION The data utilised in this report was based on: (a) notifications of all immunisation carried out in pre-school children by both the public and private sectors to the Central Immunisation Registry, Health Promotion Board (notifications of diphtheria and measles immunisation are compulsory); and (b) immunisation records kept by SHS (immunisations administered in schools and at the Immunisation Clinic, Student Health Centre of the Health Promotion Board) were captured in the SHS Computerisation System. IMMUNISATION AGAINST DIPHTHERIA, TETANUS AND PERTUSSIS Infants and pre-school children 38,565 infants and pre-school children were reported to have completed their primary immunisation course in 2002. An estimated 92% of live births completed their primary course under one year of age (Table 7.2). General practitioners immunised a total of 14,885 (38.6%) children. In 2002, a total of 41,357 booster doses were given to pre-school children. It was estimated that 93.2% of children below 2 years of age were covered by the booster programme based on Jul 2000 - Jun 2001 live-births (44,386) and assuming no mortality. School children For school entrants who had never been immunised, a primary course of two doses of diphtheria/tetanus (DT) vaccine was scheduled. In 2002, a total of 46,244 doses of DT vaccine were given to those who had received a booster more than two years before school entry or who had never received a booster. During the year, 93.1% of school entrants received boosters (Table 7.2). 7-3
Table 7.2 Diphtheria immunisation of infants, pre-school and school children, 1998-2002 Vaccination of infants and pre-school children Vaccination of school children live births@ completed primary course before one year of age (% live-births immunised) completed primary course (DT/DPT) boosters given Estimated % of pre-school children given booster doses school entrants received primary immunisation boosters given* given a booster & primary course (% school entrants immunised) 1998 45,605 43,026 (94.3) 43,696 45,326 94.3 49,793 0 44,331 44,331 (89.0) 1999 43,193 40,440 (93.9) 41,311 45,450 96.9 50,435 0 45,276 45,276 (89.8) 2000 46,631 40,216 (90.4) 40,966 37,854 94.1 50,912 0 46,527 46,527 (91.4) 2001 41775 39,450 (94.4) 39,611 38,740 92.7 50,459 0 46,725 46,725 (92.6) 2002 40,864 37,595 (92.0) 38,565 41,357 93.2 49,657 0 46,244 46,244 (93.1) Mean 43,614 40,003 (91.7) 40,830 41,887 96.0 50,251 0 45,820 45,820 (91.2) @ Source: Department of Statistics, Singapore * Figures include: (i) those given a booster dose at school entry; and (ii) those given a booster dose less than two years before school entry 7-4
In 2001, there were 3,433 (6.9%) missed vaccinees among school entrants. 761 (22.2%) of these were given boosters in 2002. For school entrants during the period 1998-2001, an average of 35% of the missed vaccinees were covered (Table 7.3). In 2002, 95.7% of the primary school leavers were given DT boosters (Table 7.4). From 1998-2002, the coverage remained high, with an average of 93.9%. Table 7.3 Coverage of missed primary I vaccinees followed up in primary II for vaccination against diphtheria, 1998-2001 missed primary one vacinees % of missed vaccinees over total new school entrants received primary immunisation in the following year received boosters in the following year % of missed vaccinees covered* % of missed vaccinees immunised over total school entrants* 1998 5,462 11.0 0 1,284 23.5 2.6 1999 4,385 8.6 0 1,299 29.6 2.6 2000 3,734 7.4 0 1,585 42.4 3.1 2001 3,433 6.9 0 1,516 44.4 3.1 Mean 4,248 8.5 0 1,421 35.0 2.9 * Coverage by School Health Service and does not include booster immunisations done by private practitioners. Table 7.4 Diphtheria and tetanus boosters given to primary school leavers 11-12 years of age, 1998-2002 Total primary VI children boosters given % of primary VI children covered 1998 40,153 37,368 93.1 1999 46,111 42,737 92.7 2000 55,554 52,582 94.7 2001 50,987 47,455 93.1 2002 53,258 50,991 95.7 Mean 49,213 46,227 93.9 7-5
IMMUNISATION AGAINST POLIOMYELITIS Infants and pre-school children 38,622 infants and pre-school children were reported to have completed their primary immunisation course in 2002. 37,615 children (92% of live births) completed their primary course before one year of age (Table 7.5). 15,043 (38.9%) children were immunised by private practitioners. In 2002, a total of 41,148 boosters were given to children below two years of age. An estimated 92.7% of children below 2 years of age were covered under the booster programme based on Jul 2000 - Jun 2001 live-births and assuming no mortality. School children In 2002, 46,052 (92.7%) school entrants were given boosters (Table 7.5). In 2001, 3,605 (7.3%) of the school entrants missed their booster doses. Of these children, 755 (20.9%) were immunised in 2002 (Table 7.6). The coverage of missed Primary I vaccinees over the period 1998-2001 constituted 2.9% of the total school entrants. During the year, 50,905 (95.6%) primary school leavers received booster doses (Table 7.7). MEASLES/MUMPS/RUBELLA IMMUNISATION Infants and pre-school children In 2002, a total of 39,954 children below two years of age were immunised against measles, mumps and rubella giving a coverage of 90% based on Jun 2000-2001 live-births (44,386) and assuming no mortality (Table 7.8). Most immunisations were carried out by restructured polyclinics, (62%) and private clinics and hospitals (37.4%). School children There were no missed vaccinees among school entrants. In 2002, the number of primary school leavers immunized was 50,700 (95.2% coverage). 7-6
Table 7.5 Poliomyelitis immunisation of infants, pre-school and school children, 1998-2002 Vaccination of infants and pre-school children Vaccination of school children live births@ completed primary course before one year of age (% live-births immunised) completed primary course boosters given Estimated % of pre-school children given booster doses school entrants received primary immunisation boosters given* given a booster and primary course (% school entrants immunised) 1998 45,605 43,084 (94.5) 43,794 45,324 94.3 49,793 0 44,191 44,191 (88.7) 1999 43,193 41,096 (95.4) 41,717 45,303 96.6 50,435 0 45,035 45,035 (89.3) 2000 46,631 40,094 (90.2) 40,914 37,481 87.0 50,912 0 46,397 46,397 (91.1) 2001 41,775 38,220 (91.5) 39,255 38,963 93.3 50,459 0 46,527 46,527 (92.7) 2002 40864 37,615 (92.0) 38,662 41,148 92.7 49,657 0 46,052 46,052 (92.7) Mean 43,614 40,022 (91.8) 40,860 41,644 92.8 50,251 0 45,640 45,640 (90.8) @ Source: Department of Statistics, Singapore. * Figures include: (i) those given a booster dose at school entry; and (ii) those given a booster dose less than two years before school entry. 7-7
Table 7.6 Coverage of missed primary I vaccinees followed up in primary II for vaccination against poliomyelitis, 1998-2001 missed primary one vaccinees % of missed vaccinees over total new school entrants received primary immunisation in the following year received boosters in the following year % of missed vaccinees covered % of missed vaccinees immunised over total school entrants* 1998 5,602 11.3 0 1,272 22.7 2.6 1999 4,515 8.9 0 1,287 28.5 2.5 2000 4,385 8.6 0 1,585 36.1 3.1 2001 3,734 7.4 0 755 20.9 3.2 Mean 4,559 9.1 0 1,225 27.1 2.9 * Coverage by School Health Service and does not include booster immunisations done by private practitioners. Table 7.7 Poliomyelitis boosters given to primary school leavers 11-12 years of age, 1998-2002 Total number of students boosters given % of students vaccinated 1998 40,153 37,305 92.9 1999 46,111 42,507 92.2 2000 55,554 52,088 93.8 2001 50,987 47,240 92.7 2002 53,258 50,905 95.6 Mean 49,213 46,009 93.5 7-8
1999 Table 7.8 Measles/mumps/rubella immunisation, 1999-2002 Private School Restructured Restructured clinics/ Health Total polyclinics hospitals hospitals Service <2 yrs 29,006 10,933 248 0 40,187 >2 yrs 611 849 350 43,310* 45,120 TOTAL 29,617 11,782 598 43,310 85,307 2000 <2 yrs 25,859 12,649 243 0 38,751 >2 yrs 913 91 53 52,952 * 54,009 TOTAL 26,772 12,740 296 52,952 92,760 2001 <2 yrs 25,697 15,007 199 0 40,903 >2 yrs 578 111 58 47,465 * 48,212 TOTAL 26,275 2002 <2 yrs 24,787 14,946 221 0 39,954 >2 yrs 789 2,723 47 51,265 * 54,824 TOTAL 25,576 17,669 268 51,268 94,778 * second dose of MMR vaccine for primary 6 students HEPATITIS B VACCINATION A total of 13,847 blood samples of antenatal women were screened at the Kandang Kerbau Women s and Children s Hospital for HBsAg and HBeAg in 2002. Of these, 325 (2.3%) were HBsAg positive and 82 (0.6%) HBeAg positive. In 2002, of 34,269 babies delivered in Kandang Kerbau Women s and Children s Hospital, Singapore General Hospital, National University Hospital, Mt Alvernia Hospital, Thomson Medical Centre and Gleneagles Hospital, 29,733 (86.8%) were vaccinated at birth (Table 7.9). 39,492 infants were reported to have completed their primary course of hepatitis B immunization below one year of age in 2002. Most immunizations were carried out by doctors at restructured polyclinics (23,990 or 60.7%) and by doctors in restructured hospitals and private practitioners (15,502 or 39.3%). The overall coverage rate for babies who have completed the full course of vaccination under one year of age remained high at 94.5% based on the live births in Jan 2002. Hepatitis B vaccination programme in secondary schools, junior colleges and centralised institutes A 4-year hepatitis B immunization programme is being carried out for secondary 3, junior college 2 and pre-university 3 students each year from 2001 to 2004. Consent was first obtained from parents for their child to participate in pre-immunisation blood screening. Each school would be visited four times within 7-9
Table 7.9 Hepatitis B vaccination of newborns in Kandang Kerbau Women s & Children s Hospital, Singapore General Hospital, National University Hospital, Thomson Medical Centre and Gleneagles Hospital, 2002 Kandang Kerbau Women s & Children s Hospital Singapore General Hospital National University Hospital Mount Alvernia Hospital Thomson Medical Centre Gleneagles Hospital Month live births vaccinated % live births vaccinated % live births vaccinated % live births vaccinated % live births vaccinated % live births vaccinated % Jan 1217 1080 88.7 162 145 89.5 241 224 93 465 369 79.4 378 363 96.0 386 353 91.5 Feb 1130 1012 89.6 142 131 92.3 196 184 93.9 439 354 80.6 321 309 96.3 325 294 90.5 Mar 1222 1039 85.0 144 124 86.1 208 206 99.0 434 380 87.6 392 356 90.8 354 318 89.8 Apr 1210 1045 86.4 163 136 83.4 202 191 94.6 486 411 84.6 372 353 94.9 355 320 90.1 May 1423 983 69.1 150 139 92.7 235 219 93.2 471 388 82.4 406 377 92.9 346 296 85.5 Jun 1201 967 80.5 138 115 83.3 226 224 99.1 385 336 87.3 359 350 97.5 316 270 85.4 Jul 1251 1050 83.9 145 125 86.2 243 219 90.1 462 415 89.8 413 391 94.7 353 313 88.7 Aug 1249 1012 81.0 195 158 81.0 248 225 90.7 463 429 92.7 435 408 93.8 360 314 87.2 Sep 1275 1044 81.9 165 148 89.7 235 213 90.6 515 457 88.7 423 398 94.1 364 320 87.9 Oct 1258 1068 84.9 164 142 86.6 245 227 92.7 522 439 84.1 498 457 91.8 399 357 89.5 Nov 1338 1144 85.5 174 154 88.5 231 225 97.4 499 413 82.8 409 359 87.8 338 309 91.4 Dec 1337 1136 85.0 163 143 87.7 236 223 94.5 491 423 86.2 218 214 98.2 354 300 84.7 Total 15,111 12,580 83.3 1,905 1,660 87.1 2,746 2,580 93.9 5,632 4,814 85.5 4,624 4,335 93.8 4,250 3,764 88.6 Note: No returns received from East Shore Hospital and Mount Elizabeth Hospital. 7-10
the calendar year (once for blood screening, three times for each dose of the vaccine at fixed intervals of one and five months). Students who missed the blood screening and immunization would be referred to the Student Health Centre. In 2002 53,382 students were screened for hepatitis B immune status. Of these, 19,249 (36.1%) of these students were tested non-immune and required hepatitis B immunization. 17,247 (89.6%) students completed a full course of 3 doses of hepatitis B vaccination. EFFECTIVENESS OF THE IMMUNISATION PROGRAMME The effectiveness of the childhood immunisation programme against poliomyelitis and diphtheria is clearly shown in Figs. 7.1 and 7.2. In 2002, no indigenous case of diphtheria, poliomyelitis, pertussis and neonatal tetanus was reported. With the implementation of the catch-up measles vaccination programme using the MMR vaccine in 1997, and the introduction of the second dose of MMR vaccine to all primary six school children in 1998, the incidence of measles remained low. It decreased sharply from 1,413 cases in 1997 to 57 in 2002 (Fig. 7.3). Rubella incidence decreased from 242 cases in 2001 to 152 in 2002. No outbreak was reported. No termination of pregnancy was carried out on account of rubella infection (Table 7.10). One case of congenital rubella was reported in a Malay infant born to a 27-year old woman who had not been vaccinated against rubella. The baby was tested positive for rubella IgM antibody at birth and had bilateral congenital glaucoma, left cataract, hearing loss and patent ductus arteriosis. Following a resurgence of mumps in 1998, due to poor protection conferred by the Rubini strain of the MMR vaccine, the disease incidence had returned to normal with 1,090 cases reported in 2002 (Table 7.11). The incidence of indigenous acute hepatitis B declined from 243 cases (9.5 per 100,000) in 1985 to 63 cases (1.9 per 100,000) in 2002 (Fig.7.4). No cases in children < 15 years had been reported since 1997. 7-11
Figure 7.1 Incidence per 100,000 population from poliomyelitis and immunisation coverage rates in Singapore, 1946-2002 100 Poliovirus vaccine type 2 to 200,000 children National immunisation programme 100 90 80 Rate per 100,000 population 10 1 70 60 50 40 30 Coverage rate in percent 20 10 0.1 46 50 54 58 62 66 70 74 78 82 86 90 94 98 02 0 Incidence per 100,000 population Immunisation coverage rate (Infants) Immunisation coverage rate (Primary school entrants) OTHER003/CMH/081003 7-12
Figure 7.2 Incidence per 100,000 population from diphtheria and immunisation coverage rates in Singapore, 1946-2002 100 Health education campaigns Immunisation compulsory 100 90 80 Rate per 100,000 population 10 1 70 60 50 40 30 C o verage rate in percent 20 10 0.1 46 50 54 58 62 66 70 74 78 82 86 90 94 98 02 0 Incidence per 100,000 population Immunisation coverage rate (Infants) Immunisation coverage rate (Primary school entrants) OTHER003/CMH/081003 7-13
Figure 7.3 Impact of the catch-up MMR vaccination programme and introduction of second dose of MMR vaccine on the incidence of reported measles cases in Singapore, 1997-2002 120 100 "Catch-up" MMR vaccination programme for all secondary and pre-university students, Jul - Nov 1997 Re porte d cases Confirm e d cases* cases 80 60 40 2nd dose of MMR vaccine introduced Enhanced epidemiological surveillance implemented 20 0 Week 1 11 21 31 41 51 9 19 29 39 49 6 16 26 36 46 4 14 24 34 44 2 12 22 32 42 52 10 20 30 40 50 1997 1998 1999 2000 2001 2002 * Measles-specific IgM antibody positive MMR002/CMH/081003 Figure 7.4 Incidence per 100,000 population from acute hepatitis B+ and immunisation coverage rates*, Singapore, 1985-2002 16 Hepatitis B vaccination for infants born to carrier mothers (Oct 1985) 120 Rate per 100,000 population 14 12 10 8 6 4 2 Hepatitis B vaccination for all newborns (Sep 1987) 100 80 60 40 20 Cov erage rate in percent 0 0 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 Rate per 100,000 Cov erage rate + Indigenous cases * For children < 1 year old Hep-B001/CMH/081003 7-14
Table 7.10 abortions done for rubella infection, 1983-2002 Total no. of abortions done for rubella infection* abortions % 1983 19,100 68 0.4 1984 22,190 77 0.3 1985 23,512 46 0.2 1986 23,035 45 0.2 1987 21,226 55 0.3 1988 20,135 56 0.3 1989 20,619 76 0.4 1990 18,669 36 0.2 1991 17,798 30 0.2 1992 17,073 21 0.1 1993 16,476 8 0.05 1994 15,690 10 0.06 1995 14,504 9 0.06 1996 14,365 15 0.1 1997 13,827 5 0.04 1998 13,838 2 0.01 1999 13,753 6 0.04 2000 13,754 2 0.01 2001 13,140 3 0.02 2002 12,749 0 0 *Not all the rubella infections were serologically confirmed. (Source: 1983-97 - Abortion Annual Statistical Report, Ministry of Health 1997-02 - Medical Audit and Accreditation Unit, Ministry of Health) 7-15
Table 7.11 Reported diphtheria, poliomyelitis, measles, acute hepatitis B, neonatal tetanus, pertussis, congenital rubella and childhood tuberculous meningitis in Singapore, 1982-2002 Diphtheria Poliomyelitis Measles Mumpsφ Rubellaφ Acute hepatitis B@ Neonatal tetanus Pertussis@@ Congenital rubella# Childhood tuberculous meningitis## 1982 6 (2) 1 (1) 1,965 - - - 1 7 3 4 1983 4 (4) 2 (2) 677 - - 10 3 7 10 1 1984 0 2 (2) 2,417 - - 10 1 1 7 0 1985 0 0 136 - - 7 0 0 3 1 1986 1 2 (2) 218 - - 5 3 9++ 3 1 1987 1 (1) 0 123 - - 6 0 9++ 2 1 1988 0 0 192 - - 2 0 11++ 0 0 1989 1 (1) 0 146 - - 4 0 1++ 2 0 1990 1 1 (1) 143 - - 1 0 8+++ 4 0 1991 1 (1) 0 216 636 51 3 0 5++ 1 0 1992 1 0 606 1,981 370 3 0 14++ 4 0 1993 0 0 665 1,962 423 2 0 1++ 4 0 1994 0 0 159 1,636 299 2 1 2++ 2 0 1995 0 0 185 786 326 0 0* 1++ 2* 2* 1996 1 (1) 0 308 765 487 3 0* 4 (1)+++ 2* 2* 1997 0 0 1,413 674 360 0 0* 2++ 0* 2* 1998 0 0 114 1,183 179 0 0* 1+ 0* 0* 1999 0 0 65 6,384 (28) 432 0 0* 1++ 2* 1* 2000 0 0 141++ 5,981+ 312+ 0 0 2 (1)+++ 0 1* 2001 0 0 61++ 1,399+ 242+ 0 0* 1+ 2* 0* 2002 0 0 57++ 1,090+ 152+ 0 0* 0 1* 1* ( ) Imported cases. φ Notifiable with effect from April 1990. @ Indigenous cases below 15 years of age. @@ All pertussis cases reported prior to 1986 were based on clinically diagnosed cases seen at the Communicable Disease Centre. + Based on clinically diagnosed cases ++ Based on laboratory confirmed cases. +++ Based on laboratory confirmed and clinically diagnosed cases. # Cases diagnosed in Toa Payoh Hospital, Kandang Kerbau Women s & Children s Hospital, Alexandra Hospital, Tan Tock Seng Hospital, Singapore General Hospital and National University Hospital. ## Below 10 years of age. Source: Annual Reports, Maternal & Child Health Service, Ministry of Health. * Source: Central Claims Processing System, Ministry of Health 7-16