Mohamed Z. Khalil

Childhood epidemiology of hepatitis A virus in Riyadh, Saudi Arabia.

The prevalence of anti-HAV antibody in children was tested in subjects presenting at clinics in Riyadh, Saudi Arabia. A blood sample was taken to test for the presence of IgG (indicating past infection) and a questionnaire concerning personal and epidemiological data relating to hepatitis A was completed. In total, 592 children aged 6 months to 15 years were suitable for the analysis. There were 179 subjects who were positive for HAV (30.2%). The proportions of subjects positive for HAV varied significantly with age (P=0.001); 32%-49% in the 7-15 age range were positive compared with 13-20% aged 6 and below. There was a significant association between a positive HAV test and social level (P=0.044), with a higher proportion positive in the low social level. Children with jaundice, personal history of jaundice or travel abroad were significantly more likely to be HAV positive (P=0.001, P=0.006, P=0.021, respectively). There was also a significant association with nationality (P=0.022), where the lowest proportion of HAV positive children were Saudi Arabian (28%). Compared to previous studies, there is a significant decrease in the HAV exposure in Saudi children with shift from high to intermediate pattern. National strategy for prevention should be evaluated.

Meningococcal serogroup C serum and salivary antibody responses to meningococcal quadrivalent conjugate vaccine in Saudi Arabian adolescents previously vaccinated with bivalent and quadrivalent meningococcal polysaccharide vaccine

Following repeated polysaccharide vaccination, reduced immune responses have been reported, but there are limited data on the mucosal response of meningococcal polysaccharide vaccine (PSV) or meningococcal conjugate vaccination. Saudi Arabian adolescents (aged 16-19 years) who had previously been vaccinated with ≥1 dose of bivalent meningococcal polysaccharide vaccine and 1 dose of quadrivalent meningococcal polysaccharide (MPSV4) were enrolled in a controlled, randomised, and modified observer-blind study (collectively termed the PSV-exposed group). The PSV-exposed group was randomised to receive either quadrivalent meningococcal conjugate vaccine (MCV4) (PSV-exposed/MCV4 group) or MPSV4 (PSV-exposed/MPSV4 group), and a PSV-naïve group received MCV4. Serum and saliva samples were collected pre-vaccination and 28 days post-vaccination. Serum serogroup-specific A, C, W and Y IgG were quantified as were salivary serogroup-specific C IgG and IgA together with total salivary IgG and IgA. For each serogroup, the post-vaccination serum geometric mean concentrations (GMCs) were significantly higher in the PSV-naïve and the PSV-exposed/MCV4 group than in the PSV-exposed/PSV4 group. For serogroup C, serum serogroup-specific IgG for the PSV-naïve group was significantly higher than both the PSV exposed groups. Higher levels of salivary serogroup C-specific IgG were found in the PSV-naïve group than those who had received two doses of polysaccharide but no significant differences were noted with regards to serogroup-specific IgA.

Safety and Immunogenicity of a Meningococcal Quadrivalent Conjugate Vaccine in Five- to Eight-Year-Old Saudi Arabian Children Previously Vaccinated with Two Doses of a Meningococcal Quadrivalent Polysaccharide Vaccine

ABSTRACT Saudi Arabian children respond poorly to 2 doses of meningococcal quadrivalent polysaccharide vaccine (MPSV4) when given before 2 years of age. This study examined whether such children were able to respond to 1 dose of quadrivalent meningococcal diphtheria toxoid conjugate vaccine (MCV4) when they were older. Saudi Arabian children 5 to 8 years of age who had previously been vaccinated with 2 doses of MPSV4 when they were under 2 years of age (termed the prior-MPSV4 group) were enrolled in a controlled, open-label, multicenter study. In the prior-MPSV4 group, children (n = 153) received 1 dose of MCV4, as did a group of age-matched meningococcal vaccine-naïve children (n = 85). Blood samples collected prevaccination and 28 days postvaccination were measured for serogroup-specific serum bactericidal antibody (SBA) levels in the presence of baby rabbit complement (rSBA) and for IgG antibody levels. Vaccine tolerability and safety were also evaluated. For all of the measured serogroups (A, C, Y, and W-135), the meningococcal vaccine-naïve participants achieved higher postvaccination rSBA geometric mean titers (GMTs) than did those in the prior-MPSV4 group. This was statistically significant for serogroup C (512 versus 167). Percentages of participants with postvaccination titers of ≥8 and with ≥4-fold increases in prevaccination to postvaccination titers appeared to be quite similar in the 2 groups. No worrisome safety signals were detected. MCV4 induced robust immune responses and was well tolerated in Saudi Arabian children who previously received 2 doses of MPSV4 as well as in those who were previously meningococcal vaccine naïve.

Immunogenicity and Safety of a Meningococcal Quadrivalent Conjugate Vaccine in Saudi Arabian Adolescents Previously Vaccinated with One Dose of Bivalent and Quadrivalent Meningococcal Polysaccharide Vaccines: a Phase III, Controlled, Randomized, and Modified Blind-Observer Study

ABSTRACT Reduced immune responses to repeated polysaccharide vaccination have been previously reported, but there are limited immunogenicity data on the use of meningococcal polysaccharide vaccine (PSV) followed by meningococcal conjugate vaccine. Saudi Arabian adolescents (aged 16 to 19 years) who had previously been vaccinated with ≥1 dose of bivalent meningococcal polysaccharide vaccine and 1 dose of quadrivalent meningococcal polysaccharide (MPSV4) were enrolled in a controlled, randomized, and modified observer-blind study (collectively termed the PSV-exposed group). The PSV-exposed group was randomized to receive either quadrivalent meningococcal conjugate vaccine (MCV4) (n = 145 PSV-exposed/MCV4 group) or MPSV4 (n = 142 PSV-exposed/MPSV4 group), and a PSV-naïve group received MCV4 (n = 163). Serum samples collected prevaccination and 28 days postvaccination were measured by baby rabbit serum bactericidal antibody (rSBA) assay, and vaccine tolerability and safety were also evaluated. For each serogroup, the postvaccination geometric mean titers (GMTs) were significantly higher in the PSV-naïve group than in either group comprised of the PSV-exposed participants. The postvaccination serogroup C rSBA GMT was significantly higher in the PSV-MCV4 group than in the PSV-MPSV4 group after adjusting for prevaccination GMTs. Although not statistically significant, similar differences were observed for serogroups A, Y, and W-135. No worrisome safety signals were detected. This study demonstrated MCV4 to be safe and immunogenic in those who had previously received polysaccharide vaccination, and it suggests that conjugate vaccine can partially compensate for the hyporesponsiveness seen with repeated doses of polysaccharide vaccine.

Clinical approach to Lymphadenopathy

Lymphadenopathy (LAP) is a common clinical finding that may be localized, limited or generalized. The enlargement of a lymph node, due to primary disease or secondary cause, is of concern to both patients and clinicians, particularly, if the underlying pathology is a malignant disease. Lymph node aspiration or biopsy for histopathological evaluation may not reveal the diagnosis due to several factors. However, a methodological approach to LAP can disclose the accurate diagnosis with minimal discomfort to the patient and in a short time. In this review article, we provide evidence-based clinical evaluation of LAP, guided by the probability of the underlying disease to assist clinicians in establishing the proper cause and hence offer appropriate management.

Follow-up of Saudi children vaccinated with Haemophilus influenzae type B vaccine.

BACKGROUND Saudi children vaccinated with a primary series of Hib vaccine (HbOC) at six weeks, three and five months have shown higher antibody titers compared to recent data from the U.S. The aim of this study was to evaluate the persistence of antibodies and to measure the immunogenicity of a booster dose of Haemophilus influenzae type b (Hib) vaccine in Saudi children. PATIENTS AND METHODS In the first phase of the trial, 210 children were divided into three groups. Group 1 received HbOC, DPT and the WHO formula of oral poliovirus vaccine (OPV); group 2 received HbOC, DPT and the FDA formula of OPV; and group 3 (control) received DPT and the WHO formula of OPV, without HbOC. Haemophilus influenzae geometric mean antibody levels after primary immunization were reported previously. In this study, blood samples were collected at 18 months (before the booster dose) and one month later to measure antibody levels against Haemophilus influenzae polysaccharide. RESULTS Following the booster doses, there was an increase in the geometric mean titers (GMTs) from 2.57 microg/mL to 39.4 microg/mL in group 1, and from 1.2 microg/mL to 48.9 microg/mL in group 2. In group 3, the GMT remained at 0.3 microg/mL. There was no significant difference in Hib GMTs after the booster dose between children given Hib vaccine with the FDA formula of DPT and OPV and those given the WHO formula. CONCLUSION Based on the high immunogenicity of the Hib vaccine in Saudi children, a booster dose is not necessary at the initial stages of immunization, and should instead be given to children in the second year of life. This option, however, needs further evaluation and close monitoring.

Immunogenicity of FDA DTP versus WHO DTP.

BACKGROUND The aim of this report was to study the immunogenicity of three doses of DTP in six-week-old Saudi infants when given either as World Health Organization (WHO) DTP or Federal Drug Administration (FDA) DTP formula. METHODS As part of the Haemophilus influenzae type b immunization research protocol, six-week-old infants were randomized into three groups to receive three doses of HbOC and WHO DTP formula, HbOC and FDA DTP formula, or in a control group to receive the usual vaccines without HbOC, at six weeks, three months and five months. Antibody levels for PRP, tetanus, diphtheria and pertussis were measured after the third dose. The results of diphtheria, pertussis and tetanus are presented in this paper. RESULTS After three doses, no difference was found between anti-PRP when given with either FDA DTP or WHO DTP formula. Also anti-tetanus and anti-diphtheria antibodies were significantly higher in the group vaccinated with HbOC and FDA DTP formula, compared to children vaccinated with WHO DTP formula. No negative interactions with other vaccines were observed after the third dose. Conclusion. Although diphtheria and tetanus antigens in the FDA formula are half the concentration in the WHO formula, they are more antigenic. There is a need for methods of potency assay to be re-evaluated.