Immunogenicity of meningococcal polysaccharide ACWY vaccine in primary immunized or revaccinated adults

Meningococcal polysaccharide (Men-Ps) vaccine immunogenicity following either primary immunization or revaccination in adults was evaluated. The study population consisted of subjects who have received tetravalent Men-Ps vaccine once (group 1) or at least twice, with a 2-6 dose range (group 2). Human leucocyte antigen (HLA)-typing was performed by polymerase chain reaction and specific immunoglobulin (Ig)G was measured by enzyme-linked immunosorbent assay. Nine months post-immunization, the percentages of individuals with levels of anti-Men-Ps IgG ≥ 2 µg/ml were comparable in both groups, with the exception of anti-Men-PsW₁₃₅ IgG, which were significantly higher in group 2. The percentage of subjects doubling IgG levels at 9 months was significantly higher in group 1. The high baseline anti-Men-Ps antibody levels negatively influenced the response to revaccination, suggesting a feedback control of specific IgG. The calculated durability of anti-Men-Ps IgG was 2·5-4·5 years, depending on the Men-Ps, following a single vaccine dose. No interference by other vaccinations nor HLA alleles association with immune response were observed. This study confirms that Men-Ps vaccine in adults is immunogenic, even when administered repeatedly, and underlines the vaccine suitability for large-scale adult immunization programmes that the higher costs of conjugate vaccines may limit in developing countries.

The Italian army standpoint on malaria chemoprophylaxis

Soldiers on duty in tropical areas are at high risk of malaria and need chemoprophylactic regimens which may ensure the best efficacy, tolerability and compliance. Current Italian Army guidelines are based on recent military experiences in tropical areas, where mefloquine prophylaxis was as well tolerated as combination treatment with chloroquine and proguanil but more effective and easier to comply with, at least among soldiers. Chloroquine alone (300 mg base once/week) is prescribed for areas without chloroquine-resistant Plasmodium falciparum, while mefloquine (250 mg once/week) is recommended for areas with chloroquine-resistance. Doxycycline is the first choice regimen for mefloquine-resistant areas and an alternative to mefloquine when this medication is contraindicated or not tolerated. The combination chloroquine-proguanil represents the alternative chemoprophylactic regimen when mefloquine and doxycycline are contraindicated or not tolerated.

Compliance and tolerability of mefloquine and chloroquine plus proguanil for long-term malaria chemoprophylaxis in groups at particular risk (the military)

An historical prospective study was performed on 5120 Italian soldiers deployed in Somalia and Mozambique in 1992-94, to determine compliance and tolerability of long-term malaria chemoprophylaxis with chloroquine plus proguanil (C + P) and with mefloquine. Compliance with C + P among 3734 soldiers on duty in Somalia for 3.8 +/- 1.8 months and with mefloquine among 1386 soldiers on duty in Mozambique for 3.4 +/- 1.5 months was 90.3% and 95.7%, respectively (P < 0.01). Chemoprophylaxis curtailment rate due to side-effects was 1.5% among C + P users and 0.9% among mefloquine users (P = NS). Compliance with chemoprophylaxis and medication curtailment rate due to side-effects did not change significantly for either C + P or mefloquine, even after 3 months of continuous prophylaxis. Chemoprophylaxis curtailment rate was significantly lower in subjects aged < or = 25 years than in older subjects (1.3% vs. 2.5% for C + P [P < 0.05] and 0.4% vs. 3.3% for mefloquine [P < 0.01]). These results further support the evidence that both C + P and mefloquine regimens may be safely used in long-term malaria chemoprophylaxis. Moreover, weekly mefloquine seems easier to perform than C + P and not to increase prophylaxis discontinuation due to side-effects. Mefloquine regimen should therefore be considered the elective chemoprophylaxis for groups at particular risk of chloroquine-resistant Plasmodium falciparum malaria and especially for young male subjects.

Prevention and morbidity of malaria in non-immune subjects; a case-control study among Italian troops in Somalia and Mozambique, 1992-1994

The impact of malaria on Italian troops taking part in 1992-1994 in the United Nations Organization humanitarian missions in Somalia and Mozambique is discussed. In Somalia, 18 cases of Plasmodium falciparum malaria occurred among 11,600 soldiers; the overall attack rate was 0.4 cases/1000/month of exposure and the risk of malaria was effectively reduced by chemoprophylaxis with chloroquine plus proguanil (C+P) (odds ratio [OR] = 0.05, 95% confidence limits [95% CL] 0.02-0.16). In Mozambique, 119 cases of P.falciparum malaria occurred among 4800 soldiers; most cases (100) occurred in the first months of deployment (late March-June 1993), with an attack rate of 17 cases/1000/month, when C+P was the recommended chemoprophylactic regimen; the remaining 19 cases occurred subsequently, with an attack rate of 1.8 cases/1000/month, after C+P was replaced by mefloquine in July 1993. Protection achieved by C+P was unsatisfactory (OR = 0.37, 95% CL 0.21-0.67), while chemoprophylaxis with mefloquine effectively reduced the risk of malaria in Mozambique (OR = 0.03; 95% CL 0.01-0.10). A significant number of malaria infections was also detected among soldiers following their return home from Somalia (147 cases) and Mozambique (40 cases); these were due mainly to P. vivax. Fifteen of 113 P. vivax primary infections imported from Somalia (13.3%) relapsed 2-13 months after the primary attack. Because of the small proportion of relapsing P. vivax tropical strains, primaquine may be limited to radical treatment of relapses or, more extensively, of all P. vivax infections, but it should not be necessarily given to all asymptomatic subjects returning from tropical endemic areas, as is generally suggested for particular groups at risk.