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Background and Objectives: The 9-valent human papillomavirus (9vHPV) vaccine Phase III immunogenicity study in 9- to 15-year-old boys and girls was extended to assess immunogenicity and effectiveness through 10 years after the last vaccine dose (NCT00943722)., Methods: Boys (n = 301) and girls (n = 971) who received three 9vHPV vaccine doses in the base study (day 1, months 2 and 6) enrolled in the extension. Serum was collected through month 126 for antibody assessments by competitive Luminex immunoassay and immunoglobulin G-Luminex immunoassay. For effectiveness analysis starting at age 16 years, genital swabs were collected (to assess HPV DNA by polymerase chain reaction) and external genital examinations conducted every 6 months. Primary analyses were conducted in per-protocol populations., Results: Geometric mean antibody titers peaked around month 7, decreased sharply between months 7 and 12, then gradually through month 126. Seropositivity rates remained ≥81% by competitive Luminex immunoassay and ≥95% by immunoglobin G-Luminex immunoassay at month 126 for each 9vHPV vaccine type. After up to 11.0 (median 10.0) years of follow-up postdose 3, there were no cases of HPV6/11/16/18/31/33/45/52/58-related high-grade intraepithelial neoplasia or condyloma in males or females. Incidence rates of HPV6/11/16/18/31/33/45/52/58-related 6-month persistent infection in males and females were low (54.6 and 52.4 per 10000 person-years, respectively) and within ranges expected in vaccinated cohorts, based on previous human papillomavirus vaccine efficacy trials., Conclusions: The 9vHPV vaccine demonstrated sustained immunogenicity and effectiveness through ∼10 years post 3 doses of 9vHPV vaccination of boys and girls aged 9 to 15 years.

Objectives: We describe the final 10-year data for the long-term follow-up study of the 4-valent human papillomavirus (4vHPV) vaccine in preadolescents and adolescents., Methods: In the base study (V501-018), 1661 sexually inactive boys and girls received the 4vHPV vaccine (early vaccination group [EVG], managed for 9.9 years) or a placebo at day 1, month 2, and month 6. Thereafter, at month 30, the placebo group (catch-up vaccination group [CVG], managed for 7.4 years) received the 4vHPV vaccine by using the same dosing schedule. Long-term anti-HPV type 6, 11, 16, and 18 immune responses were assessed. Effectiveness was estimated by calculating the incidence rate of the primary endpoints (HPV types 6, 11, 16, and 18-related disease or persistent infection)., Results: For HPV types 6, 11, and 16, 89% to 96% of subjects remained seropositive through 10-years postvaccination. The preadolescents had 38% to 65% higher geometric mean titers at month 7, which remained 16% to 42% higher at 10 years compared with adolescents. No cases of HPV type 6, 11, 16, and 18-related diseases were observed. Ten subjects had a persistent infection of ≥6 months duration with vaccine-type HPV and 2 subjects had persistent infection for ≥12 months. No new serious adverse events were reported through 10 years., Conclusions: A 3-dose regimen of the 4vHPV vaccine was immunogenic, clinically effective, and generally well tolerated in preadolescents and adolescents during 10 years of follow-up. These long-term findings support efforts to vaccinate this population against HPV before exposure., Competing Interests: POTENTIAL CONFLICT OF INTEREST: Dr Ferris has received grant support from Merck & Company Inc (Kenilworth, NJ) through his institution and personal fees for consultancy and advisory boards for Merck & Company; Drs Block and Lazcano-Ponce have received research grants from and are members of a speaker’s bureau for Merck & Company and have served as paid expert witnesses and consultants for Merck & Company; Dr Mehlsen has received funding from Merck & Company to conduct human papillomavirus–vaccine clinical trials; Dr Chatterjee has received funding from Merck & Company and GlaxoSmithKline to conduct human papillomavirus–vaccine clinical trials and served on a speaker’s bureau for Merck & Company; Dr Iversen has received compensation from Merck & Company to conduct vaccine clinical trials and for scientific advisory board fees; Drs Joshi, Chu, Krick-Likos, Saah, and Das are employees of Merck Sharp & Dohme Corporation, a subsidiary of Merck & Company and may hold stock options; the other authors have indicated they have no potential conflicts of interest to disclose., (Copyright © 2017 by the American Academy of Pediatrics.)

We evaluated the safety and immunogenicity of two doses of a live-attenuated, tetravalent dengue virus vaccine (F17/Pre formulation) and a booster dose in a dengue endemic setting in two studies. Seven children (7- to 8-year-olds) were followed for 1 year after dose 2 and then given a booster dose (F17/Pre formulation), and followed for four more years (Child study). In the Infant study, 49 2-year-olds, vaccinated as infants, were followed for approximately 3.5 years after dose 2 and then given a booster dose (F17) and followed for one additional year. Two clinically notable events were observed, both in dengue vaccine recipients in the Infant study: 1 case of dengue approximately 2.7 years after dose 2 and 1 case of suspected dengue after booster vaccinations. The booster vaccinations had a favorable safety profile in terms of reactogenicity and adverse events reported during the 1-month follow-up periods. No vaccine-related serious adverse events were reported during the studies. Neutralizing antibodies against dengue viruses 1-4 waned during the 1-3 years before boosting, which elicited a short-lived booster response but did not provide a long-lived, multivalent antibody response in most subjects. Overall, this candidate vaccine did not elicit a durable humoral immune response., (© The American Society of Tropical Medicine and Hygiene.)

A 9-valent human papillomavirus (6/11/16/18/31/33/45/52/58) VLP (9vHPV) vaccine has recently been proven highly efficacious in preventing disease associated with vaccine HPV types in a pivotal Phase III study. The demonstration of lot-to-lot consistency to confirm the reliability of the manufacturing process is a regulatory requirement for vaccine licensure in the United States. A randomized trial was conducted to demonstrate that three lots of 9vHPV vaccine elicit equivalent antibody response for all 9 vaccine types. The study required thorough planning because it required success on 27 separate statistical comparisons. An innovative statistical approach was used taking into account between-lot variance for more conservative power calculations. The study demonstrated equivalence of three lots of 9vHPV vaccine for all 9 vaccine types.

Background: We present a long-term safety, immunogenicity, and effectiveness study of a quadrivalent human papillomavirus (HPV4) vaccine., Methods: Sexually naive boys and girls aged 9 to 15 years (N = 1781) were assigned (2:1) to receive HPV4 vaccine or saline placebo at day 1 and months 2 and 6. At month 30, the placebo group (n = 482) received HPV4 vaccine following the same regimen and both cohorts were followed through month 96. Subjects ≥ 16 years were eligible for effectiveness evaluations. The primary objective was to evaluate the long-term anti-HPV6/11/16/18 serological levels. The secondary objective was to estimate vaccine effectiveness against HPV6/11/16/18-related persistent infection or disease., Results: For each of the HPV4 vaccine types, vaccination-induced anti-HPV response persisted through month 96. Among 429 subjects who received HPV4 vaccine at a mean age of 12, none developed HPV6/11/16/18-related disease or persistent infection of ≥ 12 months' duration. Acquisition of new sexual partners (among those ≥ 16 years) was ∼1 per year. Subjects receiving HPV4 vaccine at month 30 (mean age 15 years) had a similar baseline rate of seropositivity to ≥ 1 of the 4 HPV types to those vaccinated at day 1 (mean age 12 years; 1.9% [9 of 474] vs 1.7% [20 of 1157]); however, 4 of the 9 subjects vaccinated at the later age were seropositive to 3 vaccine types, indicating previous HPV exposure. No new significant serious adverse events were observed for 8 years postvaccination in both genders., Conclusions: When administered to adolescents, the HPV4 vaccine demonstrated durability in clinically effective protection and sustained antibody titers over 8 years., (Copyright © 2014 by the American Academy of Pediatrics.)

A Phase I/II observer-blind, randomized, controlled trial evaluated the safety and immunogenicity of a dengue virus (DENV) vaccine candidate in healthy Thai infants (aged 12-15 months) without measurable pre-vaccination neutralizing antibodies to DENV and Japanese encephalitis virus. Fifty-one subjects received two doses of either DENV (N = 34; four received 1/10th dose) or control vaccine (N = 17; dose 1, live varicella; dose 2, Haemophilus influenzae type b). After each vaccine dose, adverse events (AEs) were solicited for 21 days, and non-serious AEs were solicited for 30 days; serious AEs (SAEs) were recorded throughout the study. Laboratory safety assessments were performed at 10 and 30 days; neutralizing antibodies were measured at 30 days. The DENV vaccine was well-tolerated without any related SAEs. After the second dose, 85.7% of full-dose DENV vaccinees developed at least trivalent and 53.6% developed tetravalent neutralizing antibodies ≥ 1:10 to DENV (control group = 0%). This vaccine candidate, therefore, warrants continued development in this age group (NCT00322049; clinicaltrials.gov).

A 10 month-old female infant presented with one day of high fever with drowsiness and seizures. Physical examination showed meningeal irritation and mild cyanosis. The cerebrospinal fluid (CSF) profile revealed opening pressure of 27 cmH2O, closing pressure of 17 cmH2O, red blood cells 310 cells/microL, white blood cells 100 cells/microL of which 90 percents were lymphocytes, protein 391 mg/dl, sugar 0 mg/dL and blood sugar 74 mg/dl. Numerous gram positive diplococci were found on CSF Gram-stained smear. Bacterial meningitis was diagnosed and cefotaxime 300 mg/kg/day plus vancomycin 60 mg/kg/ day were given empirically. The patient developed hypotension, poor tissue perfusion, dyspnea and disseminated intravascular coagulopathy (DIC). She expired 10 hours after hospitalization. The CSF and blood culture grew out Streptococcus pneumoniae serotype 6B with the minimal inhibitory concentration (MIC) of 0.5 and 1.5 microg/mL for penicillin and cefotaxime respectively. Atypical characteristics of CSF in bacterial meningitis may cause delay in empirical antimicrobial therapy. Gram-stained smear of CSF is helpful for rapid diagnosis and proper management.

Objective: To describe the clinical course, serotype distribution and antimicrobial resistance patterns of invasive pneumococcal disease (IPD) cases in a public hospital., Material and Method: Retrospective review of IPD cases occurring from January 2004 through December 2008 was performed. Antibiotic susceptibility testing and serotyping were performed for available isolates., Results: Fifty one IPD cases occurred during the study period, of which 47 had medical records available for review. The majority of cases occurred among children under 5 years of age (23.4%) and adults over 60 years of age (36.1%). Underlying diseases were identified in 72.3% of patients. Fifty-three percent of cases were associated with pneumonia, while 17% had meningitis, and 15% had isolated bacteremia. Serotype could be determined for 15 (31.9%) isolates, and 6B was most common. Based on current antibiotic susceptibility breakpoints for meningitis, 4 of the 7 available isolates from meningitis cases were penicillin resistant and one had reduced susceptibility to cefotaxime. Among non-meningitis isolates, 96.7% were penicillin susceptible and 3.3% had intermediate susceptibility to penicillin. Overall case fatality proportion was 19%., Conclusion: At this tertiary care hospital in Bangkok, IPD has disproportionately affected young children and the elderly. High rates of penicillin resistance among meningitis cases, the most severe form of IPD, underscore the need of appropriate treatment strategies and vaccine usage.

Objective: To describe epidemiological characteristics of Acinetobacter baumannii infections and identify molecular patterns of A. baumannii isolated from the patients admitted in Phramongkutklao Hospital., Material and Method: A retrospective study on previously isolated A. baumannii from the clinical specimens submitted to the microbiology laboratory of Phramongkutklao Hospital from January to March 2008 were carried out together with molecular typing using PCR-based method. Clinical data were obtained from IC surveillance and patients' records., Results: 114 A. baumannii were isolated from 80 patients. A. baumannii was a cause of healthcare-associated infection (90%, 72 of 80 cases), colonization (7.5%), and community-acquired infection (2.5%) with mortality rate of 50%. Majority of the patients from which A. baumannii were isolated were male (58.8%), age over 60 years (56.3%), diagnosed with lower respiratory diseases (26.3%), had A. baumannii ventilator-associated pneumonia (66.7%), and admitted in medical department (57.5%) with median length of hospital stay 35 days. PDR- and MDR- A. baumannii were accounted for 67.5% and 21.1%, respectively. All isolates showed sensitive to tigecycline and colistin. Using PCR-based typing was able to distinguish 6 molecular types among 114 A. baumannii isolates. Molecular type 2 was the most common type (47.4%) and widely spread in 14 wards. Spread of clonally related isolates was found in 14 cases admitted in 8 medical wards and ICUs., Conclusion: Multiple clones of PDR- and MDR- A. baumannii were widely spread in the hospital. Clonally related A. baumannii infected 14 cases in 8 wards.

This study aimed to determine molecular patterns of Acinetobacter baumannii using a PCR-based technique with REP-1, REP-2 and M13 primers to distinguish the patients' strains and the environmental strains (condensate, endotracheal tube connector, bed rail and nurses hands). There were 67 cases of ventilator-associated pneumonia (VAP) among 600 patients using mechanical ventilators in 10 wards from March to July 2006. The incidence of VAP was 11.2% or 8.9/1,000 ventilator days with a 54.5% fatality rate. Among 19 of 22 A. baumannii VAP patients, 68.4% (13/19) had their environmental samples contaminated with A. baumannii and the most common contaminated sites were bed rails and endotracheal tube connectors (36.8% each). Multidrug resistant (MDR) A. baumannii were involved in 77.3% of A. baumannii VAP. Molecular typing of 96 A. baumannii isolates was able to differentiate A. baumannii isolates into 7 types. Type 2 was the most common and found in 77.3% (17/22) of A. baumannii VAP patients admitted in 6 of 7 wards. Identical fingerprints were found in clinical isolates and their bed rails, endotracheal tube connectors and condensates of 5 patients. The results demonstrate that multiple clones of MDR A. baumannii were widely spread in the hospital. Bed rails and contaminated endotracheal tube connectors could be potential sources of A. baumannii spread.

A cross-sectional study of 432 army college students comprising 278 medical cadets and 154 nursing students, ages ranging from 15 to 26 years, was conducted in 2001 to determine the seroprevalence of hepatitis A virus (HAV) antibody. Serum specimens were tested for HAV antibody by a commercial enzyme immunoassay method. Anti-HAV was detected in 14.0%, 17.5%, and 15.3% of medical cadets, nursing students, and the total cohort, respectively. There was no statistically significant difference in seroprevalence between medical cadets and nursing students. Increasing prevalence of HAV correlated with increasing age. Significantly higher seroprevalence was detected in students from provinces outside of Bangkok compared to those who were from Bangkok (18.7% vs. 9.8%). The highest HAV seroprevalence was observed in subjects from the northeastern region of Thailand, suggesting that this region may be associated with greater risk for infection and should be the focus of preventive health strategies.

Background: This study was designed to evaluate the efficacy and safety of cold-adapted influenza vaccine, trivalent (CAIV-T) against culture-confirmed influenza in children 12 to <36 months of age during 2 consecutive influenza seasons at multiple sites in Asia., Methods: In year 1, 3174 children 12 to <36 months of age were randomized to receive 2 doses of CAIV-T (n = 1900) or placebo (n = 1274) intranasally > or =28 days apart. In year 2, 2947 subjects were rerandomized to receive 1 dose of CAIV-T or placebo., Results: Mean age at enrollment was 23.5 +/- 7.4 months. In year 1, efficacy of CAIV-T compared with placebo was 72.9% [95% confidence interval (CI): 62.8-80.5%] against antigenically similar influenza subtypes, and 70.1% (95% CI: 60.9-77.3%) against any strain. In year 2, revaccination with CAIV-T demonstrated significant efficacy against antigenically similar (84.3%; 95% CI: 70.1-92.4%) and any (64.2%; 95% CI: 44.2-77.3%) influenza strains. In year 1, fever, runny nose/nasal congestion, decreased activity and appetite, and use of fever medication were more frequent with CAIV-T after dose 1. Runny nose/nasal congestion after dose 2 (year 1) and dose 3 (year 2) and use of fever medication after dose 3 (year 2) were the only other events reported significantly more frequently in CAIV-T recipients., Conclusions: CAIV-T was well tolerated and effective in preventing culture-confirmed influenza illness over multiple and complex influenza seasons in young children in Asia.

Objective: Administration of a quadrivalent HPV-6/ 1/16/18 vaccine to 16- to 26-year-old women was highly effective in preventing HPV-6/ 1/16/18-related cervical/vulvar/vaginal precancerous lesions and genital warts. As the risk of acquiring HPV significantly rises after sexual debut, HPV vaccines should have the greatest benefit in sexually naive adolescents. We evaluated the tolerability and immunogenicity of quadrivalent vaccine in males and females 9 to 15 years of age through 18 months postenrollment., Methods: In this randomized, double-blind trial, 1781 sexually naive children were assigned (2:1) to quadrivalent HPV-6/11/16/18 vaccine or saline placebo administered at day 1 and months 2 and 6. Serum neutralizing anti-HPV-6/11/16/18 responses were summarized as geometric mean titers (GMTs) and seroconversion rates. Primary analyses were done per-protocol (subjects received 3 doses, had no major protocol violations and were HPV type-specific seronegative at day 1). Adverse experiences were collected by diary card., Results: At month 7, seroconversion rates were > or =99.5% for the 4 vaccine-HPV-types. GMTs and seroconversion rates in boys were noninferior to those in girls (P < 0.001). At month 18, > or =91.5% of vaccine recipients were seropositive, regardless of gender. A higher proportion of vaccine recipients (75.3%) than placebo recipients (50.0%) reported one or more injection-site adverse experiences following any vaccination. Rates of fever were similar between vaccination groups. No serious vaccine-related adverse experiences were reported., Conclusions: In 9- to 15-year-old adolescents, the quadrivalent vaccine was generally well tolerated and induced persistent anti-HPV serologic responses in the majority of subjects for at least 12 months following completion of a three-dose regimen. The vaccine durability supports universal HPV vaccination programs in adolescents to reduce the burden of clinical HPV disease, particularly cervical cancer and precancers.

Objectives: To develop a less expensive assay to calculate HIV-1 viral load for use in resource-limited countries., Material and Method: An In-house One-tube-one-step Viral Load Assay (IOVA) was developed by using real-time PCR-based with TaqMan probe. Primers and probe were designed from the conserved region of sequences from all HIV subtypes. A standard curve was generated from reference virus in various dilutions. IOVA was applied on 105 HIV-positive and 25 HIV-negative samples and compared with the results from ROCHE AMPLICLOR., Results: IOVA measured HIV RNA in the samples ranging from 125 to 2 x 10(6) copies/mL. The coefficient of variation of intra- and inter-assay ranged from 0.68% to 7.89%. The sensitivity, specificity, positive and negative predictive values were 92%, 100%, 100% and 79.5% respectively. The parallel quantitative analysis showed high correlation (r=0.95) between IOVA and AMPLICOR., Conclusion: A new HIV-1 viral load assay was developed and validated. It was reliable and less expensive.

Antibodies of all four dengue virus serotypes were detected by hemagglutination inhibition (HI) in 97% of 2,000 infants' cord sera at the time of delivery. In comparison with 250 mother-infant's paired sera, we found that 53% of the infants' serum HI titers were higher than those of the mother's. The mother/infant IgG subclasses 1, 2, 3, and 4 titers were 53.1/87.0, 8.4/11.7, 0.14/0.11, and 1.1/1.0 mg/dL, respectively. In 18 months of follow-up of 100 infants studied, we observed that antibody to dengue virus disappeared in 3% by two months of age, in 19% by four months of age, in 72% by six months of age, in 99% by nine months of age, and in 100% by 12 months of age, with a half-life of 41 days. We conclude that the antibodies to dengue virus disappeared in the first year of life. We suggest that the most appropriate age for vaccination with a live-attenuated dengue vaccine in an endemic area is one year of age.

We report a case of vertical transmission of dengue infection in an infant. The mother's was a term pregnancy with a history of chronic hypertension. She presented with high fever of 3 days duration 5 days prior to delivery. Her initial complete blood count showed platelet count of 64,000/mm3. Dengue hemorrhagic fever was diagnosed 2 days later and symptomatic treatment was given. During labor her platelets dropped to 11,000/mm3 and platelet concentrate was given. Cesarean section was performed due to prolonged second stage of labor. Her infant was normal at birth except for petechiae on the left thigh. The child's platelet count was 34,000/mm3 and low grade fever was detected on the first day. Clinical sepsis was suspected and antibiotic treatment was started and continued for 4 days until all the cultures came back as negative. Both mother and her baby made an uneventful recovery and were discharged 6 days after delivery with normal platelet counts. Maternal blood was positive for IgM antibody to dengue virus. Both cord blood and the baby's blood were positive for dengue virus serotype 2 by PCR.

The objective of this study was to determine changes in Th1/Th2 cytokine production at the cellular level which occur during the progression of HIV-1 subtype E infection in Thai children born to HIV-1 subtype E infected mothers. Mitogen stimulated whole blood cultures from 12 uninfected and 27 HIV-1 subtype E infected Thai children were stained intracellularly with fluorescein labelled monoclonal antibodies against Interleukin (IL)-2 and IFN-gamma (Th1 cytokines) and IL-4 (Th2 cytokine). Additionally, co-staining of CD4+ and CD8+ T cells was performed. Results were analyzed by two and three color flow cytometry. The percentage of IFN-gamma expressing cells in CD4+ T cells was increased in HIV-1 subtype E infected Thai children with mild and moderate immunosuppression (Immunological categories 1 + 2, Centers for Diseases Control and Prevention (CDC) staging system, 1994). The percentages of IFN-gamma expression was continuously enhanced accompanied by remaining preserved in the proportion of IL-2 producing T cells in HIV-1 subtype E infected Thai children with severe immunosuppression (Immunological category 3, CDC staging system, 1994). The percentages of IFN-gamma expression was continuously augmented whereas the proportion of IL-2 producing T cells remained unchanged in HIV-1 subtype E infected Thai Children with severe immunosuppression (immunological category 3, CDC staging system, 1994). The percentage of Th2 cytokine producing cells within the CD4+ ad CD8+ T cells increased in HIV-1 subtype E infected individuals and showed a significant difference in HIV-1 subtype E infected Thai children with AIDS compared with uninfected infants. These results suggest that in vertically acquired HIV-1 infection with severe immunosuppression, the percentages of IL-2 producing CD4+ T cell was consistent but the percentages of IL-4 and IFN-gamma producing cell were increased. Similar results were found for CD8+ T cells in which IL-4 producing cells were increased in conjunction with a remaining in the number of IL-2 producing cells in HIV-1 subtype E infected Thai children. Thus, changes in the Th1 and Th2 cytokine pattern during HIV-1 infection may contribute to the prognosis of HIV disease in children.

Rhesus-human reassortant tetravalent (RRV-TV) oral rotavirus vaccine was given at the same time as oral poliovirus vaccine (OPV) or inactivated parenteral poliovirus vaccine (IPV) to Thai infants at 2, 4 and 6 months of age. Sera for rotavirus antibody studies were taken prior to and one month after each vaccination. After the first dose of vaccine at 2 months of age, 37% of the infants receiving rotavirus vaccine with IPV but only 10% of those receiving it with OPV showed a seroconversion by rotavirus IgA ELISA antibody test (p < 0.001). Likewise, neutralizing antibody seroconversion rates in initially seronegative subjects to rhesus rotavirus type 3 (RRV-3) after the first dose of RRV-TV vaccine were higher if the vaccine was given with IPV (74%) than if given with OPV (39%) (p = 0.0069). After the second and third doses of vaccine, the rotavirus IgA ELISA and RRV-3-neutralizing antibody response rates were not different between groups. Development of neutralizing antibodies to human rotavirus serotypes 1, 2 and 4 in the first seven months of life in vaccinees receiving rotavirus vaccine with OPV tended to occur at a lower rate than in those receiving rotavirus vaccine with IPV but the antibody levels were not significantly different at 7 months of age. Poliovirus type 2 and type 3 antibody responses were not different in infants receiving the rotavirus vaccine with OPV as compared with infants receiving only OPV. The mean poliovirus type 1 antibody level was slightly but not significantly lower at 5 and 7 months of age in infants that received both rotavirus vaccine and OPV.(ABSTRACT TRUNCATED AT 250 WORDS)

In a randomized double blind placebo-controlled study, the rhesus-human reassortant tetravalent oral rotavirus vaccine (dose 4 x 10(4) plaque-forming units) was evaluated in Thai infants immunized at ages 2, 4 and 6 months. To investigate dose responses and to compare vaccine-induced and naturally acquired rotavirus immunity in the study population blood specimens were collected before and 1 month after each vaccination and at 12 months of age. No adverse reactions attributable to the vaccine were detected in the vaccinees. Sixty-three of 94 (67%) vaccine recipients showed a seroconversion in rotavirus IgA enzyme-linked immunosorbent assay antibodies after one or more doses, whereas only 15 of 93 (16%) placebo-vaccinated control children showed an IgA enzyme-linked immunosorbent assay antibody response, suggestive of natural rotavirus infection, between 2 and 7 months of age. By measuring rhesus rotavirus-neutralizing antibodies a seroconversion was detected in 49% of the vaccinees and 14% of the controls between 2 and 7 months of age. The geometric mean titers of neutralizing antibodies to human rotavirus serotypes 1, 2, 3 and 4 after the completion of vaccinations and at 12 months of age were higher in the vaccinees than in the controls. It is concluded that, even though maternally acquired rotavirus antibodies are commonly present, the rhesus-human reassortant tetravalent vaccine is immunogenic in many Thai infants ages 2 to 6 months. The immunogenicity of this vaccine is enhanced by multiple doses.

Enhanced potency inactivated poliovirus vaccine (EIPV), combined with diphtheria-tetanus-pertussis (DTP) vaccine, was compared with oral poliovirus vaccine (OPV) regarding immunogenicity in Thai infants, vaccinated at 2, 4 and 6 months of age. EIPV induced significantly higher seroconversion rates than OPV to all 3 poliovirus types after the second and third immunization. After 3 doses of each vaccine, at 7 months of age, all infants receiving EIPV proved seropositive for poliovirus type 1, type 2 and type 3 neutralizing antibodies, whereas of those receiving OPV, 9% remained seronegative (titre < 1:4) for type 1 (p = 0.0042) and 11% for type 3 (p = 0.0013). All participating children were given an additional dose of OPV at the age of 9 months and tested again at 12 months of age. At that point, virtually all infants had poliovirus neutralizing antibodies, but the geometric mean titres to each poliovirus type were significantly higher in the vaccinees who had received EIPV. It is concluded that the greater immunogenicity of EIPV vis-à-vis 3 doses of OPV may be biologically significant for protection against poliovirus types 1 and 3 in countries where cases of poliomyelitis occur in young children. These findings warrant considering EIPV, alone or in combination with OPV, for an immunization programme in Thailand and similar countries in the future.