Natural Booster Research Articles

Diagnostics biologiques de la coqueluche

Whooping cough is a respiratory infection particularly severe for infants. The agents of the disease are the bacteria Bordetella pertussis and Bordetella parapertussis. Before vaccination, disease affected in majority children. Because of the high circulation of the bacteria, adolescents and adults were regularly in contact with the bacteria and had natural boosters. Forty years after generalized vaccination in some countries, a change in the transmission of the disease is observed. Children are not infected between 2 and 5–10 years of age (depending on the vaccine used and the vaccine calendar) because they were vaccinated in their infancy. However, adolescents and adults are becoming susceptible because they do not receive any vaccinal or natural boosters. They can infect and contaminate infants too young to be vaccinated. Clinical symptoms in adolescents and adults, previously vaccinated or infected, are very variable and for this reason biological diagnosis are now necessary to confirm infection. These diagnostics are culture, PCR and serology.

IgG avidity to distinguish secondary from primary measles vaccination failures: prospects for a more effective global measles elimination strategy

The nearly 40-year long debate on the relevance of secondary measles vaccination failure has been inconclusive because a feasible method for the assessment of the duration of immunity has been lacking. Even if a two-dose measles vaccination policy is now universally endorsed, WHO still officially adheres to the view that a single successful measles vaccination, without natural boosters, induces a lifelong immunity and deems secondary failures epidemiologically irrelevant – in the belief that the latter are rare and do not participate in the transmission chain. A recently published study on measles-IgG avidity, which allows for separation of secondary from primary vaccination failures, tentatively showed that the official view does not necessarily hold true. The results may have wide implications on global measles eradication efforts. The potential of IgG avidity measurement in complex postvaccination measles epidemiology is discussed.

Épidémiologie de la coqueluche en France

Despite very high coverage levels for more than 30 years with a vaccine whose protective efficacy has been confirmed by surveillance data and outbreak investigation, pertussis has not been eliminated in France. Data from a multicentric hospital-based study performed in 1993–94, together with data from the hospital-based paediatric sentinel surveillance network Renacoq has provided some insight into the current epidemiology of the disease. They also provided some clues about the reasons for the persistence of the circulation of Bordetella pertussis. The scarcity of natural boosters, resulting from the reduction of the transmission of the disease by the vaccination, and the limited duration of vaccine-induced protection to about 8 to 10 years, induced the building up of a reservoir of susceptible older children and young adults. They represent, especially in regions with very high vaccination coverage, the main source of infection for young infants, before they have completed the full series of primary vaccination. This finding led to the introduction in 1998 in the French immunisation schedule of a booster dose, based on the newly marketed acellular pertussis vaccines. The follow-up of the epidemiologic impact of this measure, in particular on the incidence of the disease in the first year of life, is being performed by the paediatricians and bacteriologists voluntarily participating in the Renacoq surveillance network.

Tuberculin skin reactivity in Italian military recruits tested in 1996-1997.

In 1996-1997 data was collected and a Mantoux tuberculin test performed in 2882 Italian military recruits aged 18-23 years in order to establish the prevalence of tuberculin reactivity. In addition, the annual risk of infection, defined as the probability that a non-infected individual would be infected during the following year, was calculated. Of the 2882 recruits, 513 had received a BCG vaccination, the remaining 2369 had not. The overall prevalence of subjects with a tuberculin skin reaction size >5 mm (the cut-off point for positivity corresponding to the antimode in the reaction size frequency curve) was 6.1% (144/2369). The prevalence of skin reactivity increased with age but remained similar when related to area of residence, duration of father's school education and family size. The same general trend was observed if the standard pre-established cut-off point of 10 mm was used. In this case the overall prevalence of a positive skin reaction was 4% (95/2369). The annual risk of infection was 0.3% for a prevalence of tuberculin skin reactivity of 6.1% (cut-off point 5 mm) and 0.19% for a prevalence of 4% (cut-off point 10 mm). Analysis of the population sample vaccinated with BCG showed a lack of correlation between the positive reaction after vaccination reported retrospectively by the subject and the current skin reaction observed by the physician in this study (K = 0.254). Moreover, a significant difference was observed between the skin reaction in subjects vaccinated with BCG in 1993-1994 (average size 12.5 mm) and that of subjects vaccinated in 1995-1996 (average size 10.1 mm, P<0.01), probably as a consequence of mycobacteria circulating in the general population which act as a natural booster in people already vaccinated with BCG. A booster effect of tuberculin in Mantoux assays also cannot be excluded.

Long-term follow-up of hepatitis A vaccination in children

We conducted this follow-up study to evaluate the long-term immunogenicity of an inactivated hepatitis A vaccine in children. Ninety-six children who had seroconversion to antibody to HAV (anti-HAV) after receiving a three-dose schedule of inactivated hepatitis A vaccine were enrolled into this study. Sixty months after the initial vaccination, all vaccinees who received annual follow-up still had protective levels of anti-HAV. The geometric mean titer (GMT) of anti-HAV, peaking at month 7 (4133 mIU/mL), kept declining throughout the follow-up period. The GMTs in months 12, 24, 36, 48 and 60 were 1722, 896, 896, 645 and 403 mIU/mL, respectively. Nine of the vaccinees were hepatitis B virus carriers. Their anti-HAV titers tended to be lower than those of the remaining vaccinees at all time-points, but the difference was not significant ( p>0.05). Natural booster was noted in one vaccinee during the follow-up period. In conclusion, inactivated hepatitis A vaccine is safe and immunogenic in children, the duration of protection against HAV infection is longer than five years.

Vaccine-induced measles virus antibodies after two doses of combined measles, mumps and rubella vaccine: a 12-year follow-up in two cohorts

In Finland, a two-dose vaccination programme against measles, mumps and rubella (MMR) was begun in 1982. The programme with high coverage (97–98%) has eliminated these three diseases from Finland. The aim of the present study was to follow up the kinetics of measles virus antibodies in MMR vaccinated cohorts. We have followed the kinetics of measles virus antibody levels induced by vaccination in the same individuals immunized with their first MMR vaccine in 1982. After 12 years 80% of the original children remained available for sampling. Antibodies to measles virus were measured by haemagglutination inhibition (HI) and plaque reduction neutralization (NT) techniques. The primary dose induced 99.4% seroconversion for measles with a geometric mean HI antibody titre (GMT) of 1 269 (±219), equivalent to 4304 mIU (milli-International Units) ml −1 in group A. The 12-year follow-up specimens showed a measles seropositivity rate of 100% as assayed with the HI and NT tests with a mean HI antibody titre of 1 39 (±54), equivalent to 624 mIU ml −1. The vaccination-induced measles virus antibodies decline in the absence of natural booster infections. It is important to follow how long the protection achieved by the present vaccine programme will last after elimination of indigenous measles.

Physical Activity as a Natural Antioxidant Booster and its Effect on a Healthy Life Span

The recent Surgeon General's report (U.S. Department of Health and Human Services, 1996) promotes regular physical activity to enhance health. A possible mechanism by which physical activity contributes to a healthy life span is via enhanced antioxidant status. The purpose of this paper is to summarize findings from human studies on life span, health, antioxidants, and the effectiveness of physical activity as a natural antioxidant booster. Epidemiological studies concur that some antioxidants are inversely related to mortality. A single bout of exercise elevates some antioxidant enzyme and coenzyme activities. Regular physical activity enhances some antioxidants; however, strenuous exercise may diminish others. Results generally show that antioxidants play a mediating role in the way in which physical activity positively affects a healthy life span.

NEONATAL MEASLES IN HOKKAIDO, JAPAN

NEONATAL MEASLES IN HOKKAIDO, JAPAN

Hepatitis B vaccine trial in neonates

AbstractIn an attempt to interrupt perinatal and postnatal transmission of hepatitis B virus (HBV) infection, hepatitis B vaccine trials were initiated in October 1981 in Taiwan, starting in neonates of hepatitis B e antigen (HBeAg)‐positive hepatitis B surface antigen (HBsAg) carrier mothers and extending to neonates of non‐carrier mothers. All neonates had received a four‐dose schedule of Pasteur plasma‐derived hepatitis B vaccine. Among neonates of HBeAg‐positive HBsAg carrier mothers, the protective efficacy rate of vaccination was 75% in those who received vaccine alone and 90% in those who received vaccine plus hepatitis B immunoglobulin (HBIG) at birth. Among neonates of HBeAg‐negative HBsAg carrier mothers, the protective efficacy rate was 100% whether they had received vaccine alone or vaccine plus HBIG at birth. The protective efficacy rate was also 100% in neonates of non‐carrier mothers. During 6–9 years of long‐term follow‐up, 12 (6%) responsive vaccinees of HBeAg‐positive carrier mothers, one (2%) child of HBeAg‐negative carrier mothers and one child (0.4%) of non‐carrier mothers had seroconverted to antibody to hepatitis B core antigen (anti‐HBc) positivity. ‘Natural booster’ phenomenon, defined as a spontaneous sharp rise in serum antibody to HBsAg (anti‐HBs) titres in the absence of anti‐HBc and HBsAg, was observed in 7% of vaccinees whose mothers were HBeAg‐positive, 6% of vaccinees whose mothers were HBeAg‐negative HBV carriers, and 8% in vaccinees of non‐HBV carrier mothers. None of the responsive vaccinees had seroconverted to HBsAg. Thus, in the first decade of life, the protective efficacy in neonates who responded to plasma‐derived hepatitis B vaccine was 100%.

Long-term follow-up of hepatitis B vaccination in susceptible hospital personnel

Two hundred and sixty-seven susceptible hospital personnel who had been randomly divided into three groups to receive different doses (5 micrograms, 2 micrograms or 1 microgram) of a plasma-derived hepatitis B vaccine on a four-dose schedule were investigated annually for 4 years. Of them, 251 were vaccine responders. The percentages of persistence of antibody to hepatitis B surface antigen (anti-HBs) in these 3 groups were 95.5% (84/88), 92.3% (72/78) and 95.3% (81/85), respectively (P greater than 0.05). During the follow-up period, 12 of 21 (57.1%) responders with low anti-HBs titres (10-100 miu/mL) and 3 of 48 (6.3%) responders with medium anti-HBs titres (101-1000 miu/mL) were found to be anti-HBs seronegative, while none of the 182 candidates with high anti-HBs levels (greater than 1000 miu/mL) lost their anti-HBs. The 4 year cumulative rate of natural booster in the responders was 11.6% (29/251). None of the candidates became HBsAg positive during the follow-up period. This study revealed that low dose hepatitis B vaccine can provide satisfactory immunogenic response and long-term efficacy in Chinese adults and that the persistence of immunogenicity is not related to the vaccine dose but to the candidate's own initial anti-HBs response.

Perfecting the impellers of natural gas boosters

Perfecting the impellers of natural gas boosters