Comparison of safety and immunogenicity of a Vi polysaccharide typhoid vaccine with a whole-cell killed vaccine in Malaysian Air Force recruits.

OBJECTIVE: To carry out a comparative study of the safety and immunogenicity of Vi polysaccharide vaccine against whole-cell killed (WCK) typhoid vaccine. METHODS: The study was carried out on young adult recruits (aged 18-25 years) of the Malaysian Air Force. A total of 125 subjects received the Vi polysaccharide vaccine and 114 received the WCK vaccine. FINDINGS: The Vi vaccine was significantly less reactogenic than the WCK vaccine with regard to systemic and local reactions. Following administration of the Vi vaccine, seroconversion rates (defined as the percentage of subjects with a 4-fold rise of baseline antibody level) of 75.5% and 67% were observed at 2 weeks and 6 weeks, respectively, after immunization, compared with 25% and 31.3% among recipients of the WCK vaccine. Of the 110 Vi vaccinees with serological data, 21 (19%) had high, seroprotective, pre-immunization levels of anti-Vi antibodies (> or = 1 microgram/ml). The majority of subjects in this group came from a region in Malaysia which is known to have high typhoid endemicity. Interestingly, these antibody levels were boosted considerably following administration of vaccine at a level that was 5-fold higher than in subjects with low pre-immunization levels. In contrast, the seroconversion rates in those receiving the Vi vaccine were higher in subjects with low pre-immunization levels of anti-Vi antibodies (76-84%), compared to those with protective levels of > or = 1 microgram/ml prior to immunization (48-57%). CONCLUSIONS: The study reaffirms the safety and efficacy of the Vi polysaccharide vaccine and identifies a hitherto unrecognized advantage in its use, i.e. it is a potent immunogen that boosted considerably the protective antibody levels among a significant number of immunologically sensitized individuals living in typhoid-endemic regions.

Seroetiology of acute lower respiratory infections among hospitalized children in Beijing.

BACKGROUND: Little is known of the etiology of childhood acute lower respiratory infections in China, where the use of antimicrobials is indiscriminate. Trials to change such a policy require etiologic data, especially on the bacteria most relevant to these common diseases. METHODS: One hundred consecutive infants and children from 3 months to 14 years of age with symptoms and signs compatible with acute lower respiratory infections were studied prospectively in the largest pediatric hospital in Beijing from February to May, 1997. Blood culture, thorax radiography and paired sera for 20 microbiologic assays were taken, and the course of illness was monitored uniformly. Disease severity was graded. RESULTS: In 24 cases there was evidence only of bacterial etiology, and in 5 solely viral agents were found; 3 children probably had a mixed bacterial-viral infection. Surprisingly no pneumococcal infection was detected, Mycoplasma pneumoniae (n = 21), Haemophilus influenzae type b (n = 8) and Chlamydia pneumoniae (n = 7) being the dominant bacteria. All children recovered. CONCLUSIONS: Routine use of antimicrobials for these patients seems unjustified. Serologic evidence for the H. influenzae type b etiology is encouraging in terms of vaccination, but confirmatory studies are needed.

The incidence of vaccine preventable influenza-like illness and medication use among Pakistani pilgrims to the Haj in Saudi Arabia.

Over the 33-day duration of the 1999 Haj in Saudi Arabia, we collected daily health status reports for 2070 Pakistani pilgrims over 13 years of age, 54% of whom had elected to receive influenza vaccine immediately before departing for the Haj. We calculated vaccine preventable outcome incidence as the difference in attack rates between vaccinated and unvaccinated persons. The incidences of vaccine preventable influenza-like illness (sore throat in combination with cough or fever of at least 38 degrees C), fever, and any symptom of upper respiratory infection were 22, 17, and 24 per 100 pilgrims per Haj. For every 100 persons who attended the Haj, 17 had a course of antibiotics and 23 had a course of nonprescription cold medication that was preventable with influenza vaccine use. Influenza leads to significant morbidity and medication use among Haj pilgrims. Vaccine against influenza should be considered for pilgrims before entry into Saudi Arabia.

Detection by PCR of human papillomavirus genotypes in cervical lesions of Senegalese women.

In order to analyse human papillomavirus (HPV) infection in the Senegalese population, HPV DNA was sought in 65 women with evidence of cervical cytological abnormality and in 72 pregnant women. Ninety-four percent of the patients were positive for HPV DNA as compared to 24% of pregnant women. HPV 16 was detected in cervical smears in 42% of cases, HPV 18 in 39%, HPV 6 in 26%, HPV 11 in 15%, HPV 45 in 10%, HPV 52 in 3%, and HPV 31, HPV 33 and HPV 68 in 1.5%. HPV 16 and HPV 18 were detected in 16% and 7% respectively of pregnant women. HPV DNA of unknown type was detected in 6% of cases, and multiple HPV infections were observed in 28% of cases. Low risk genital HPVs (6/11) were detected in smaller proportions (17%) among high grade squamous intraepithelial lesions (SILs) than the low grade SILs (43%). High risk HPVs (16/18) were detected in high proportions both in low and high grade SIL lesions, though the highest frequency (70%) was observed among patients with high grade lesions. In conclusion, the results confirm that HPV infections are frequent in Senegal and that HPV 18 and 45 are detected in a high proportion of patients in Africa.

Detection of antibodies against human papillomavirus (HPV) type 16 virions by enzyme-linked immunosorbent assay using recombinant HPV 16 L1 capsids produced by recombinant baculovirus.

The L1 major capsid protein of human papillomavirus type 16 (HPV-16) was expressed in Sf-21 insect cells with a recombinant baculovirus. Virus-like particles obtained were purified and used to develop an enzyme-linked immunosorbent assay for detection of anti-HPV-16 antibodies in sera from 76 women with evidence of genital HPV infection and 79 controls. HPV-16-infected individuals developed antibodies directed at HPV-16 virions since reactivity against recombinant HPV-16L1 capsids was observed in 50% of them compared with only 6% in the general adult population. However, some cross-reactivities with sera from women infected with others HPV types were observed.

Detection of antibodies to L1, L2, and E4 proteins of human papillomavirus types 6, 11, and 16 by ELISA using synthetic peptides.

Antibodies against eight synthetic peptides spanning different epitopes located on L1, L2, and E4 proteins of human papillomavirus (HPV) types 16, 6, and 11 were examined in sera from 73 women infected by HPV and from 139 healthy controls. Only three of these peptides were reactive. Two located on proteins L2 and E4 of HPV 16 seem type specific since antibodies to these peptides were detected, respectively, in 21% and 15% of the HPV 16 infected patients and in 2.5% and none of women infected by other HPVs. The third peptide located on the L1 protein of HPV 6 bears a common epitope since antibodies to this peptide were detected not only in 85% of women infected by HPV 6 or 11, but also in 82% of women infected by other HPVs, and in 74% and 71% of the control groups (10-12-year-old children and adults, respectively). In conclusion, none of the peptides investigated seems useful to develop ELISAs for serological diagnosis of HPV infection.

Etiology of acute sporadic hepatitis in adults in Senegal and Tunisia.

Markers for acute hepatitis A, B, C and E virus infections were examined in the sera of 72 patients suffering from acute hepatitis in Senegal and Tunisia. Hepatitis B was responsible for 36% and hepatitis C for 21% of the cases. Acute hepatitis A was not diagnosed. HEV infection was not observed in Senegal and represents only 4% of the acute hepatitis cases in Tunisia.

Twelve-year follow-up study of hepatitis B immunization of Senegalese infants.

Numerous studies have documented the efficacy and safety of plasma-derived and recombinant hepatitis B vaccines. However, little is known about the long-term protection of hepatitis B vaccine, when anti-HBs declines to low or undetectable levels. This study reports results from a 9-12-year period follow up of infants immunized against hepatitis B in Senegal. At the end of the follow-up period anti-HBs were detected in 81% of children who received a booster dose at school age and in 68% of those who did not. HBsAg was detected in 19% of infants from the control group compared to only 2% of immunized infants, corresponding to a protective efficacy of 88%. The results show that long-term protection against HBsAg carriage of hepatitis B vaccination is very high and that a booster dose at school age does not significantly increase this protection.

Detection of hepatitis B virus DNA by polymerase chain reaction in vaccinated and non-vaccinated Senegalese children.

An hepatitis B immunization programme was initiated in Senegal in 1978, and infants included in this controlled study have been followed for a period of 2-12 years after immunization. During this period HBV infections have been observed both in vaccinated and non-vaccinated infants. The polymerase chain reaction was used to search for HBV DNA sequences in the sera of 153 children with evidence of serum markers of past or present HBV replication. Amplified HBV DNA sequences were detected in 93% of the HBsAg positive individuals, in 58% of those only positive for antiHBc antibodies and in 7.8% of antiHBs and antiHBc positive infants. The results confirm the high efficiency and long-lasting effectiveness of HB vaccine.

Detection of hepatitis B virus DNA by polymerase chain reaction in HBsAg negative Senegalese patients suffering from cirrhosis or primary liver cancer.

The polymerase chain reaction was used to search for hepatitis B virus (HBV)-DNA sequences in the sera of HBsAg-negative Senegalese patients suffering from liver cirrhosis or liver cancer. Amplified HBV-DNA sequences were detected by hybridization with a digoxigenin-labelled HBV-DNA probe. HBV-DNA was detected in 17% of HBsAg negative Senegalese subjects from the general population and in 44% and 58% of the patients suffering from cirrhosis or primary hepatocellular carcinoma (PHCC) respectively. In the control group, amplified HBV-DNA was detected in 25% of the subjects without HBsAg and anti-HBs antibodies, and in 6% of subjects positive for anti-HBs antibodies. This study confirmed the hypothesis that there is an etiologic link between HBV and PHCC in HBsAg-negative patients.