An epidemic of measles in southern Greenland 1951; measles in virgin soil. IV. The significance of specific prophylaxis

Measles in pregnant women: A systematic review of clinical outcomes and a meta-analysis of antibodies seroprevalence

OBJECTIVES

Pregnant women represent a category at high risk of severe measles infection, that negatively affects the fetus as well. A systematic review of clinical outcomes of measles infection in gravid subjects and a meta-analysis of antibodies prevalence among pregnant women was conducted.

METHODS

MEDLINE and EMBASE databases were searched up to 18 June 2018. The screening focused on: (i) articles describing the outcome of measles in pregnancy, synthesized in a descriptive fashion; (ii) articles addressing the measles seroprevalence in cohorts of gravid women, analysed quantitatively.

RESULTS

Twenty-nine articles met inclusion criteria. A total of 420 cases of measles in gravid subjects were described, from 1941 to 2012. Among women, 18 deaths (4.3%) occurred, and the most frequent complication was pneumonia (75/420, 17.9%). Prematurity was the most important complication concerning fetal outcomes (55 out of 410 cases with available data, 13.4%). The random-effects pooled seroprevalence of measles in 20,546 gravid women worldwide was 89.3% (95% CI: 87.3-91.1%), that decreased, although not in a statistically significant way, over time (p = 0.54).

CONCLUSIONS

Measles infection in pregnancy is dangerous both for the mother and the foetus. Antibody seroprevalence among gravid women on a global scale is lower than the herd immunity threshold.

Post-exposure passive immunisation for preventing measles

BACKGROUND

Measles outbreaks continue to occur in countries with high vaccination coverage. Passive immunisation is generally considered to prevent measles in someone who is not immune and has been exposed to infection. Estimates of effectiveness have varied and no minimum effective dose has been determined.

OBJECTIVES

To assess the effectiveness and safety of intramuscular injection or intravenous infusion of immunoglobulins (passive immunisation) for preventing measles when administered to exposed susceptible people before the onset of symptoms.

SEARCH METHODS

We searched CENTRAL (2013, Issue 7), MEDLINE (1946 to July week 5, 2013), CINAHL (1981 to August 2013) and EMBASE (1974 to August 2013).

SELECTION CRITERIA

We included randomised controlled trials (RCTs), quasi-RCTs and prospective, controlled (cohort) studies if: participants were susceptible and exposed to measles, polyclonal immunoglobulins derived from human sera or plasma were administered intramuscularly or intravenously as the only intervention in at least one group and the number of subsequent measles cases was measured. We excluded studies of other sources of immunoglobulins.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and critically appraised the included studies. We attempted to contact study authors for missing information. We described the results of studies not included in meta-analyses.

MAIN RESULTS

We included one RCT, two quasi-RCTs and 10 cohort studies (3925 participants). No studies were rated as low risk of bias for all criteria. Critical appraisal was constrained by a lack of information in most studies. The overall quality of the evidence was moderate.Seven studies (1432 participants) assessed cases of measles after immunoglobulin versus no treatment. Heterogeneity was explained by subgrouping according to the blood product used as an approximation of dose of immunoglobulin. When given within seven days of exposure, immunoglobulins were effective at preventing measles: gamma globulin (risk ratio (RR) 0.17, 95% confidence interval (CI) 0.08 to 0.36), convalescent serum (RR 0.21, 95% CI 0.15 to 0.29 to RR 0.49, 95% CI 0.44 to 0.54) and adult serum (RR 0.52, 95% CI 0.45 to 0.59). The differences in the effectiveness of different blood products were supported by studies not included in the meta-analysis and by two studies (702 participants) that found gamma globulin more effective than serum (RR 0.56, 95% CI 0.46 to 0.69).Based on three studies (893 participants) immunoglobulin was effective at preventing death due to measles compared to no treatment (RR 0.24, 95% CI 0.13 to 0.44).Two studies included measles vaccine alone among the intervention groups. Meta-analysis could not be undertaken. Both studies suggested the vaccine was more effective than gamma globulin.No serious adverse events were observed in any of the included studies, although reporting of adverse events was poor overall. Non-serious adverse events included transient fever, rash, muscle stiffness, local redness and induration.

AUTHORS' CONCLUSIONS

Passive immunisation within seven days of exposure is effective at preventing measles, with the risk for non-immune people up to 83% less than if no treatment is given. Given an attack rate of 45 per 1000 (per the control group of the most recent included study), gamma globulin compared to no treatment has an absolute risk reduction (ARR) of 37 per 1000 and a number needed to treat to benefit (NNTB) of 27. Given an attack rate of 759 per 1000 (per the attack rate of the other included study assessing gamma globulin), the ARR of gamma globulin compared to no treatment is 629 and the NNTB is two.It seems the dose of immunoglobulin administered impacts on effectiveness. A minimum effective dose of measles-specific antibodies could not be identified.Passive immunisation is effective at preventing deaths from measles, reducing the risk by 76% compared to no treatment. Whether the benefits of passive immunisation vary among subgroups of non-immune exposed people could not be determined.Due to a paucity of evidence comparing vaccine to passive immunisation, no firm conclusions can be drawn regarding relative effectiveness.The included studies were not specifically designed to detect adverse events.Future research should consider the effectiveness of passive immunisation for preventing measles in high-risk populations such as pregnant women, immunocompromised people and infants. Further efforts should be made to determine the minimum effective dose of measles-specific antibodies for post-exposure prophylaxis and the relative effectiveness of vaccine compared to immunoglobulin.

Severe measles: a reappraisal of the role of nutrition, overcrowding and virus dose

The factors predisposing to severe measles, which accounts for a considerable fraction of the high infant and child mortality in the third world, are re-examined. The conviction that protein-energy-malnutrition (PEM) aggravates measles is challenged by findings of prospective community-based studies. It was found that severe measles was not associated with PEM but frequently accompanied overcrowding in Guinea-Bissau. Secondary cases fared worse than index patients. Among adequately nourished hospitalised African children, immunological and radiological parameters, together with the effects of age and HLA antigens, were closely related to sickness and death in measles. This variation in case fatality rate does not appear to be simply explained by age-dependent host reactions or differences in medical care. The hypothesis which fits most of the observed facts postulates that the transmission of a large inoculum of virus particles to susceptible children is an important cause of severe disease. The implication of this interpretation is that specific measles control, and not only improvements in nutrition, is important in high risk areas for a reduction of measles mortality. It is further suggested that health policy should promote those social changes which limit intense exposure to measles virus.