Dose Of Inactivated Poliovirus Vaccine Research Articles

Safety and Immunogenicity of Inactivated Poliovirus Vaccine Made From Sabin Strains: A Phase II, Randomized, Positive-Controlled Trial

The production of Sabin inactivated poliovirus vaccine (IPV) can reduce biosafety requirements in the posteradication/post-oral poliovirus vaccine (OPV) era. We conducted a phase II, randomized, positive-controlled trial to assess the safety and immunogenicity of Sabin IPV. The test groups (A, B, and C) received 3 doses of high, middle, and low D antigen (D Ag) of Sabin IPV at ages 2, 3, and 4 months, respectively. Infants in 2 control groups, group D and group E, received 3 doses of trivalent OPV and conventional IPV (cIPV), respectively, on the same schedule as that of groups A, B, and C. Serum samples were collected before and 30 days after the administration of the third dose. In total, 500 infants were randomly assigned to 5 groups, and 449 infants completed the vaccine series. No serious adverse events were associated with vaccinations. After 3 doses, the seroconversion rates in groups A, B, C, D, and E were 100%, 97.8%, 96.6%, 100%, and 90.1%, respectively, for type 1 poliovirus; 97.7%, 95.7%, 78.7%, 100%, and 90.1%, respectively, for type 2; and 98.8%, 98.9%, 93.3%, 100%, and 97.8%, respectively, for type 3. Sabin IPV has good safety characteristics. The seroconversion rates for type 1 poliovirus (most appropriate concentration, 15 D Ag units [DU]), type 2 (32 DU), and type 3 (45 DU) Sabin IPV were similar to those of the OPV and cIPV control groups. NCT01056705.

Randomized controlled study of fractional doses of inactivated poliovirus vaccine administered intradermally with a needle in the Philippines

Comparison of a fractional inactivated poliovirus vaccine (IPV) dose administered intradermally (ID) to a full dose administered intramuscularly (IM). Healthy Filipino infants were randomized to receive IPV as either a fractional (1/5(th)) dose ID by needle injection or a full dose IM at 6, 10, and 14 weeks and a booster at 15-18 months of age. Pre- and post-vaccination anti-polio 1, 2, and 3 titers were estimated. Adverse events were monitored throughout the study. Following primary series vaccination, anti-polio 1, 2, and 3 titers were ≥8 (1/dil) in 99-100% of participants, and the ID route was non-inferior to the IM route. Depending on the study group, antibody persistence was detected in 83-100% of participants, and the booster dose resulted in a strong anamnestic response in all groups. The incidence of adverse events in each group was similar, except for injection-site erythema (higher in the ID group). Primary series and booster vaccination of a fractional IPV dose administered by the ID route was highly immunogenic and well tolerated. These data confirm the medical validity of using fractional ID doses of IPV. The programmatic feasibility of implementing affordable mass vaccination programs based on this delivery mode has yet to be established.

Poliovirus

Despite marked progress in global polio eradication, the threat of polio importation into the United States remains; therefore, all children should be protected against the disease. The standard schedule for poliovirus immunization remains 4 doses of inactivated poliovirus vaccine at 2, 4, and 6 through 18 months and 4 through 6 years of age. The minimum interval between doses 1 and 2 and between doses 2 and 3 is 4 weeks, and the minimum interval between doses 3 and 4 is 6 months. The minimum age for dose 1 is 6 weeks. Minimal age and intervals should be used when there is imminent threat of exposure, such as travel to an area in which polio is endemic or epidemic. The final dose in the inactivated poliovirus vaccine series should be administered at 4 through 6 years of age, regardless of the previous number of doses administered before the fourth birthday, and at least 6 months since the last dose was received.

Fractional Doses of Inactivated Poliovirus Vaccine in Oman

We conducted a clinical trial of fractional doses of inactivated poliovirus vaccine administered to infants in Oman, in order to evaluate strategies for making the vaccine affordable for use in developing countries. We compared fractional doses of inactivated poliovirus vaccine (0.1 ml, representing one fifth of a full dose) given intradermally with the use of a needle-free jet injector device, with full doses of vaccine given intramuscularly, with respect to immunogenicity and reactogenicity. Infants were randomly assigned at birth to receive either a fractional dose or a full dose of inactivated poliovirus vaccine at 2, 4, and 6 months. We also administered a challenge dose of monovalent type 1 oral poliovirus vaccine at 7 months and collected stool samples before and 7 days after administration of the challenge dose. A total of 400 infants were randomized, of whom 373 (93.2%) fulfilled the study requirements. No significant baseline differences between the groups were detected. Thirty days after completion of the three-dose schedule, the rates of seroconversion to types 1, 2, and 3 poliovirus were 97.3%, 95.7%, and 97.9%, respectively, in the fractional-dose group, as compared with 100% seroconversion to all serotypes in the full-dose group (P=0.01 for the comparison with respect to type 2 poliovirus; results with respect to types 1 and 3 poliovirus were not significant). The median titers were significantly lower in the fractional-dose group than in the full-dose group (P<0.001 for all three poliovirus serotypes). At 7 months, 74.8% of the infants in the fractional-dose group and 63.1% of those in full-dose group excreted type 1 poliovirus (P=0.03). Between birth and 7 months, 42 hospitalizations were reported, all related to infectious causes, anemia, or falls, with no significant difference between vaccination groups. These data show that fractional doses of inactivated poliovirus vaccine administered intradermally at 2, 4, and 6 months, as compared with full doses of inactivated poliovirus vaccine given intramuscularly on the same schedule, induce similar levels of seroconversion but significantly lower titers. (Current Controlled Trials number, ISRCTN17418767.)

Randomized Controlled Clinical Trial of Fractional Doses of Inactivated Poliovirus Vaccine Administered Intradermally by Needle‐Free Device in Cuba

As part of an evaluation of strategies to make inactivated poliovirus vaccine (IPV) affordable for developing countries, we conducted a clinical trial of fractional doses of IPV in Cuba. We compared the immunogenicity and reactogenicity of fractional-dose IPV (0.1 mL, or 1/5 of a full dose) given intradermally using a needle-free jet injector device compared with full doses given intramuscularly. Subjects were randomized at birth to receive IPV at 6, 10, and 14 weeks. A total of 471 subjects were randomized to the 2 study groups, and 364 subjects fulfilled the study requirements. No significant differences at baseline were detected. Thirty days after completing the 3-dose schedule of IPV, 52.9%, 85.0%, and 69.0% of subjects in the fractional-dose IPV arm seroconverted for poliovirus types 1, 2, and 3, respectively, whereas 89.3%, 95.5%, and 98.9% of subjects in the full-dose IPV arm seroconverted for poliovirus types 1, 2, and 3, respectively (all comparisons, P < .001). The median titers of each poliovirus serotype were significantly lower in the intradermal arm than in the intramuscular arm (P < .001). Only minor local adverse effects and no moderate or serious adverse events were reported. This large-scale evaluation demonstrates the feasibility of fractional doses of IPV given intradermally as an antigen-sparing strategy but also shows that IPV given to infants at 6, 10, and 14 weeks of age results in suboptimal immunogenicity (especially for the fractional-dose arm).

Molecular characterization of poliovirus isolates from children who contracted vaccine-associated paralytic poliomyelitis (VAPP) following administration of monovalent type 3 oral poliovirus vaccine in the 1960s in Hungary

Hungarian children were immunized with monovalent oral poliovaccine (mOPV) delivered at 6-week intervals in the order Sabin 1, Sabin 3, Sabin 2, from 1959 until 1992. During that period, 90 cases of vaccine-associated paralytic poliomyelitis (VAPP) were reported, 52 of which were associated with Sabin 3-related virus (76% of VAPP cases with virologic data). Because of renewed interest in type 3 mOPV (mOPV3), molecular methods were used to reanalyze 18 of the Sabin 3-related isolates from 15 VAPP patients, confirming the original identification. All isolates had the U472C 5'-untranslated region (5'-UTR) substitution associated with reversion to neurovirulence, and from zero to seven nucleotide substitutions in the virus protein 1 (VP1) region. No evidence was found for prolonged mOPV3 replication in the VAPP patients or for spread of Sabin 3-related viruses beyond close vaccinee contacts. The VAPP diseases were prevented by a single dose of inactivated poliovirus vaccine from 1992 to 2006 in Hungary, as proved by continuous surveillance of acute flaccid paralysis.

Randomized Trial of Inactivated and Live Polio Vaccine Schedules in Guatemalan Infants

The immunogenicity of inactivated poliovirus vaccine (IPV) in developing countries is not well documented. This study compared the immune response to IPV with that to oral poliovirus vaccine (OPV) in Guatemalan infants. This was an open-label, randomized comparison of IPV only, OPV only, or IPV followed by OPV in Guatemalan public health clinics. Serum samples were tested for neutralizing antibodies, and stool samples were tested for Sabin strain polioviruses. Seropositivity rates 2 months after 2 doses of IPV were 98%-100% for polio types 1, 2, and 3 and were 97.1%, 99.3%, and 92.1% for OPV-only recipients (P<.001 for the response to type 3). One month after the third dose, 100% of IPV-only recipients had protective antibodies against all 3 types, compared with 99%, 100%, and 97% against polio types 1, 2, and 3 respectively, among recipients of OPV only. Infants who received IPV only had higher geometric mean titers than infants who received OPV only. Maternal antibodies lowered the final antibody responses to IPV but did not prevent the development of protective levels of antibody. Of 191 stool samples from infants who received IPV only, 5 (2.6%) were positive for poliovirus vaccine strains. IPV alone and IPV followed by OPV are safe and effective for Guatemalan infants.

Serologic Response to Inactivated Poliovirus Vaccine: A Randomized Clinical Trial Comparing 2 Vaccination Schedules in Puerto Rico

The World Health Organization (WHO) recommends the discontinuation of oral poliovirus vaccine after eradication of wild poliovirus. Studies assessing inactivated poliovirus vaccine (IPV) immunogenicity in tropical countries, using the WHO Expanded Programme on Immunization (EPI) schedule, have been limited. We conducted a randomized clinical trial in Ponce, Puerto Rico. Infants were assigned to 1 of 2 study arms: those in the EPI arm received IPV at 6, 10, and 14 weeks of age, and those in the US arm received IPV at 2, 4, and 6 months of age. Neutralizing antibody titers against poliovirus types 1, 2, and 3 were tested on serum specimens obtained before administration of the first dose of IPV and 28-45 days after administration of the last dose of IPV. Seroconversion rates for the EPI (n=225) and US (n=230) arms, respectively, were 85.8% and 99.6% for poliovirus type 1 (P<.001), 86.2% and 100% for poliovirus type 2 (P<.001), and 96.9% and 99.1% for poliovirus type 3 (P=.08). Seroconversion rates were lower among infants in the EPI arm who had high maternal antibody levels for all 3 poliovirus types (P<.001). The EPI schedule resulted in lower seroconversion rates for poliovirus types 1 and 2. These results are relevant for tropical countries planning to use IPV in a posteradication environment.

Effect of Different Vaccination Schedules on Excretion of Oral Poliovirus Vaccine Strains

Inactivated poliovirus vaccine (IPV) is believed to induce significantly lower mucosal immunity than oral poliovirus vaccine (OPV). Most of the data supporting this were generated before enhanced IPV (eIPV) was introduced. Excretion of poliovirus by OPV recipients can be used to assess intestinal immunity. We studied polymerase chain reaction amplification of viral complementary DNA from the stool of children vaccinated with either OPV alone or eIPV. Of first-time OPV recipients, 92% excreted virus after 1 week, and 81% excreted virus after 3 weeks. Prior vaccination with OPV reduced the number to 22% and shortened the duration of virus excretion (to 5% after 3 weeks). Two doses of IPV reduced the number of poliovirus-positive 1-week samples (to 76%), the duration of shedding (to 37% at 3 weeks), and the quantity of excreted virus. This suggests that IPV-vaccinated communities are partially protected from the spread of poliovirus. Further enhancement of IPV potency may lead to even higher levels of mucosal immunity.

Safety and immunogenicity of a booster dose of inactivated poliovirus vaccine produced in vero-cells

Statens Serum Institut has developed a new vero-cell culturing technique for the manufacturing of inactivated poliovirus vaccine (IPV). This technique implies that the cultivation of cells and poliovirus is performed in a medium free of materials of animal origin and free of antibiotics. In a double-blind randomised clinical trial, IPV vero manufactured by this new technique was compared to conventionally produced IPV mkc. One hundred and twenty-nine (129) healthy adult volunteers were given booster vaccinations of IPV vero (65) or IPV mkc (64). Both vaccines were well tolerated and resulted in excellent booster responses. No statistically significant differences were seen between the study groups.

Serological response and poliovirus excretion following different combined oral and inactivated poliovirus vaccines immunization schedules

A controlled study was conducted in Karachi, Pakistan to compare humoral and mucosal immune responses against polioviruses in infants who received oral poliovirus vaccine (OPV) at birth and at 6, 10, and 14 weeks according to the Expanded Program on Immunization (EPI) with infants who received either three doses of inactivated poliovirus vaccine (IPV) at 6, 10, and 14 weeks together with OPV or one additional dose of IPV at 14 weeks together, with the last dose of OPV. A total of 1429 infants were enrolled; 24-week serum specimens were available for 898 infants (63%). They all received a challenge dose of OPV type 3 at 24 weeks of age. The addition of three doses of IPV to three doses of OPV induced a significantly higher percentage of seropositive children at 24 weeks of age for polio 1 (97% versus 89%, P<0.001) and polio 3 (98% versus 92%) compared to the EPI schedule. However, the one supplemental dose of IPV at 14 weeks did not increase the serological response at 24 weeks. Intestinal immunity against the challenge dose was similar in the three groups. Combined schedules of OPV and IPV in the form of diphtheria–pertussis–tetanus–IPV vaccine (DPT–IPV) may be useful to accelerate eradication of polio in developing countries.

Controlled trial of immune response of preterm infants to recombinant hepatitis B and inactivated poliovirus vaccines administered simultaneously shortly after birth

AIMThe study was conducted to evaluate the immunogenicity of an early, extra dose of enhanced inactivated poliovirus vaccine (IPV) administered simultaneously with recombinant hepatitis B vaccine (HBV) to preterm infants...

Impact of the sequential poliovirus immunization schedule: a demonstration project

Objective: Researchers for this project evaluated compliance with the sequential poliovirus immunization schedule that uses inactivated poliovirus vaccine (IPV) for the first 2 doses of the polio immunization series, and assessed immunization coverage rates before and after implementation of this schedule at 6 public health clinics serving 1 county in Georgia. Design: Immunization histories for 3 birth cohorts of infants were compared: (1) the baseline cohort, born January 1 through June 30, 1995; (2) the evaluation cohort, born January 1 through June 30, 1997, after implementation of the schedule change; and (3) the dose-3 cohort, born August 1 through November 30, 1996 (i.e., old enough to be eligible for a third dose of poliovirus vaccine following implementation of the sequential schedule). Results: Following implementation of the new poliovirus immunization recommendations, 94% (534 of 567) of infants who received their first dose of poliovirus vaccine by age 3 months received IPV. Among these infants, 99.6% (532 of 534) were also up to date (UTD) for first doses of diphtheria and tetanus toxoids and acellular pertussis vaccine (DTP1/DTaP1), 99.6% (532 of 534) were UTD for first doses of hemophilus influenza type b (Hib 1), and 98.6% (527 of 534) had received at least one dose of Hepatitis B. Among infants visiting the clinics for their first or second dose of poliovirus vaccine, DTaP/DTP, and/or Hib, 76% received 3 or 4 simultaneous injections. In the dose-3 cohort, 78% (145 of 185) of infants who received a third dose of poliovirus vaccine had received 2 doses of IPV and 1 dose of oral poliovirus vaccine. Conclusions: Compliance with the recommended use of IPV for the first 2 poliovirus immunization doses as part of the sequential schedule was very high in this low-income and ethnically diverse population. Furthermore, the need for additional injections did not impede the delivery of recommended childhood immunizations.

Recommended Childhood Immunization Schedule—United States, January–December 1999

The annual Recommended Childhood Immunization Schedule of the American Academy of Pediatrics (AAP), the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC), and the American Academy of Family Physicians (AAFP) is issued in January of each year. Several significant changes for the 1999 Schedule have been made since publication of the 1998 Schedule.1This report provides the 1999 Schedule and delineates the changes, including those in the footnotes, as follows:1. Rotavirus vaccine (Rv) at 2, 4, and 6 months of age is recommended. Details of the AAP recommendations for rotavirus vaccination were published in the December 1998 issue ofPediatrics.2 Rv is shaded in theSchedule to indicate that implementation of the recommendation for routine use will require reconciliation of related economic issues, as noted in the AAP statement.2. Inactivated poliovirus vaccine (IPV) is recommended at 2 and 4 months of age. For the third and fourth doses of poliovirus vaccine, either IPV or oral poliovirus vaccine (OPV) can be administered. Details of the AAP recommendations regarding this change are given in the statement in this issue of Pediatrics.33. The manufacturer of Recombivax HB (Merck and Co, Inc, West Point, PA) has standardized the dose of this hepatitis vaccine to 5 μg for children from birth through 19 years of age regardless of maternal hepatitis B surface antigen carrier status. The change was made to avoid the confusion that occasionally occurred due to the availability of multiple dose formulations of this vaccine product. Children who have received a 2.5-μg dose of Recombivax for any or all the recommended doses are considered adequately immunized and no additional doses need to be administered. The other available hepatitis B vaccine, Engerix B (SmithKline Beecham, Pittsburgh, PA), also has a standard dose (10 μg) for all children from birth through 19 years of age. The vaccines are interchangeable when given in the doses recommended by the manufacturers.4. Acellular pertussis vaccines combined with diphtheria and tetanus toxoids (DTaP) are listed on the Schedule as the recommended product for pertussis vaccination. Whole-cell pertussis-containing vaccines (DTP) remain acceptable, as noted in the footnote.A fourth acellular pertussis-containing vaccine (Certiva [North American Vaccines, Beltsville, MD]) has been approved by the Food and Drug Administration (FDA) for immunization of infants and children. Clinical data to support the superiority of one DTaP product in comparison to the others are not available, and therefore the four approved DTaP products are considered equally acceptable. Additional questions regarding acellular pertussis vaccines have been addressed in a recent article in AAP News.45. The footnote in the Schedule pertaining toHaemophilus influenzae type b (Hib) vaccine has been modified to indicate that currently available DTaP/Hib combination products should not be used for the primary immunization series of infants unless approved by the FDA for the specific ages. The use of one such product in infants has resulted in suboptimal antibody responses.56. Minor changes to clarify recommendations have been made in the measles–mumps–rubella vaccine (MMR) and varicella footnotes, and the numbers (1, 2, and 3) for the respective doses of hepatitis B vaccine in the Schedule have been omitted to make the information consistent with that for other vaccines.Detailed recommendations for the use of the vaccines routinely indicated during infancy, childhood, and adolescence are given in the1997 Red Book,6 AAP statements (www.aap.org), and ACIP statements (www.cdc.gov/nip) on specific vaccines, and the respective manufacturers' package inserts.

Immune response of infants to fractional doses of intradermally administered inactivated poliovirus vaccine

Seventy eight infants aged 6–8 weeks received either two doses of 0.1 ml of inactivated poliovirus vaccine (IPV) intradermally 8 weeks apart (group A) or three doses 4 weeks apart (group B). Pre- and 4 weeks post-immunization serum samples were tested for the presence and titer of neutralizing antibody to poliovirus types 1, 2 and 3. The seroconversion rates to poliovirus types 1, 2 and 3 were 90, 70 and 97%, respectively, among infants in group A and 90, 80 and 98%, respectively, in group B; in children without pre-existing maternal antibody, seroconversion rates were 100% to all three poliovirus serotypes in both groups. These rates were comparable to those in children receiving five doses of OPV or two doses of intramuscular IPV. Intradermal administration of fractional doses of IPV may be a less expensive alternative for use in developing countries.

Paralytic Poliomyelitis—United States, 1980-1994

The Advisory Committee on Immunization Practices (ACIP) recently recommended a sequential vaccination schedule of two doses of inactivated poliovirus vaccine (IPV) followed by two doses of oral poliovirus vaccine (OPV) for routine vaccination of children in the United States (1). ACIP revised its recommendation for routine poliovirus vaccination for three reasons: 1) paralytic poliomyelitis attributable to indigenously acquired wild poliovirus has not occurred in the United States since 1979 (2), 2) progress toward global eradication of poliomyelitis has reduced the risk for importation of wild poliovirus into the United States (3), and 3) vaccine-associated paralytic poliomyelitis (VAPP) continues to occur. ACIP has recommended that implementation of this new vaccination schedule begin in early 1997. This report summarizes both the epidemiology of paralytic poliomyelitis in the United States reported during 1980-1994 and provisional reports for 1995-1996 and updates the estimated risk for VAPP. These findings indicate that the overall estimated risk for VAPP has remained constant.

Sequential and Combined Use of Inactivated and Oral Poliovirus Vaccines: Dolj District, Romania, 1992-1994

To determine the feasibility of a vaccination strategy that would reduce the risk of vaccine-associated paralysis while retaining a barrier against the spread of wild poliovirus, a 2-year project was undertaken using enhanced-potency inactivated poliovirus vaccine (IPV) administered at 2 and 3 months of age followed by doses of both IPV and oral poliovirus vaccine (OPV) administered at 4 and 9 months of age. Vaccination coverage by 12 months of age with three or more doses of IPV and two doses of OPV among 16,566 infants eligible for vaccination was > 95% and > 80%, respectively. Among 51 children from whom blood samples were obtained 45 days after their third dose of IPV and first dose of OPV, 100% had serum neutralizing antibodies (reciprocal titer > or = 10) to all three poliovirus types. No cases of paralytic poliomyelitis due to either wild or vaccine-related strains were reported. The project demonstrated the feasibility, safety, and high immunogenicity of sequential use of IPV followed by OPV in Romania.

Humoral and Mucosal Immunity in Infants Induced by Three Sequential Inactivated Poliovirus Vaccine-Live Attenuated Oral Poliovirus Vaccine Immunization Schedules

The relative immunity induced by sequential administration of inactivated poliovirus vaccine (IPV) produced in human diploid cells and live attenuated oral poliovirus vaccine (OPV) was evaluated by randomization of 510 infants to receive IPV and OPV sequentially according to one of three experimental schedules, IPV only, or OPV only. The antibody response to two IPV doses was lower than expected. However, for each of the IPV-OPV sequential schedules, the first OPV dose significantly enhanced seroconversion rates and geometric mean microneutralization antibody titers. Three months after the final dose, 96%-99%, 99%-100%, and 81%-100% of infants had antibodies to poliovirus types 1, 2, and 3, respectively, and subjects with two or more prior OPV doses were significantly less likely than those with none or one prior OPV dose to excrete virus in feces after an OPV challenge. Sequential IPV-OPV immunization is now recommended for routine use in the United States. The optimal schedule consists of two IPV doses followed by two OPV doses.

Inactivated Poliovirus Vaccine and Vaccine-Associated Paralytic Poliomyelitis

To the Editor. —In the design of their model evaluating cost vs benefit of the inactivated poliovirus vaccine (IPV) and oral poliovirus vaccine (OPV) schedule, Dr Miller and colleagues1state that the Delphi panel assumed that no immunodeficient persons receiving a vaccination will avoid vaccine-associated paralytic poliomyelitis (VAPP) by receiving 2 doses of IPV before OPV. Yet, in their review of 105 cases of VAPP, Nkowane et al2noted that, of the 11 immunodeficient recipients with VAPP, 3 contracted it on the third or fourth OPV dose. These data suggest a reduction of VAPP by 27% among immunodeficient recipients if the schedule of 2 IPV doses and 2 OPV doses is adopted. Were these data considered by the Delphi panel prior to design of the model?

Immunogenicity of a supplemental dose of oral versus inactivated poliovirus vaccine

In many developing countries, the immunogenicity of three doses of live, attenuated, oral poliovirus vaccine (OPV) is lower than that in industrialised countries. We evaluated serum neutralising antibody responses in 368 children aged 6 months and 346 children aged 9 months in Côte d'lvoire who had previously received three doses of 0PV at 2, 3, and 4 months of age, and who were then randomised to receive a supplemental dose of OPV or enhanced-potency inactivated poliovirus vaccine (IPV) at the time of measles vaccination. Although both vaccines increased seroconversion to all three poliovirus types, antibody responses were greater in the IPV group. Among children with no detectable antibody at baseline, IPV was 2 to 14 times more likely than OPV to induce seroconversion (type 1, 80% vs 40% at 6 months [p<0·001] and 81% vs 14% at 9 months [p<0·001]; type 3, 76% vs 22% at 6 months [p<0·001], and 67% vs 5% at 9 months [p<0·001]). Among children with detectable antibody at baseline, IPV was 1·4 to 7 times more likely than OPV to elicit 4-fold or more rises in antibody titre (p<0·01). Geometric mean titres (GMTs) to all three poliovirus types were also consistently higher among IPV recipients than in 0PV recipients when measured 4-6 weeks and 13-17 months after vaccination. Administration of a supplemental dose of IPV or 0PV, which requires no additional visits or changes in the existing immunisation schedule, might improve protection against paralytic poliomyelitis in communities with suboptimum seroconversion rates after three doses of OPV.