[Epidemiological analysis of immunity against vaccine-preventable diseases: rubella, measles, mumps and chickenpox]

The risk factors of exposure to rubella among pregnant women in Zaria 2013

INTRODUCTION

rubella virus usually causes a mild disease, but maternal infection early in pregnancy often leads to birth defects known as congenital rubella syndrome (CRS). Rubella remains poorly controlled in Africa despite being a vaccine preventable disease. The objective of this study was to determine the risk factor of expose of rubella and prevalence of rubella IgG antibodies among pregnant women in Zaria. The results of this study will provide data which may be used to advise the government of Kaduna State on the need to include rubella vaccine in the free routine immunization particularly for women of childbearing age.

METHODS

a cross-sectional study was carried out. Pregnant women attending antenatal clinics from three different health facilities in Zaria. A questionnaire was administered, to determine the proportion of pregnant women vaccinated and the sera of these women were tested for rubella IgG antibody using commercially produced enzyme-linked immunosorbent assay (ELISA) Kit. Statistical variables were compared with univariate (frequencies) bivariate (chi- square), multivariate analyses (logistic regression). A p-value of < 0.05 was considered significantly associated at 95% confidence intervals.

RESULTS

of the 246 pregnant women screened, 222 (90.2%) were positive for rubella IgG. Prevalence was highest 82/222 (36.9%) among age group 20-24 years. Those positive of those who had completed secondary school education were 104/222 (46.8%) A large number among those who tested positive with 197/222 (88.7%) were married. The Hausa tribe 155/222 (69.9%) had the highest positivity for rubella IgG. Only 2 (0.9%) women claimed to have received rubella vaccine and 159/222 (71.6%) women were seropositive for IgG among the unemployed group.

CONCLUSION

the serological evidence of rubella virus is an indication that rubella is endemic in Nigeria. Nigeria should include rubella vaccination in the routine immunization exercise for women before they get pregnant to reduce the risk of CRS.

Streptococcal Immunity Is Constrained by Lack of Immunological Memory following a Single Episode of Pyoderma

The immunobiology underlying the slow acquisition of skin immunity to group A streptococci (GAS), is not understood, but attributed to specific virulence factors impeding innate immunity and significant antigenic diversity of the type-specific M-protein, hindering acquired immunity. We used a number of epidemiologically distinct GAS strains to model the development of acquired immunity. We show that infection leads to antibody responses to the serotype-specific determinants on the M-protein and profound protective immunity; however, memory B cells do not develop and immunity is rapidly lost. Furthermore, antibodies do not develop to a conserved M-protein epitope that is able to induce immunity following vaccination. However, if re-infected with the same strain within three weeks, enduring immunity and memory B-cells (MBCs) to type-specific epitopes do develop. Such MBCs can adoptively transfer protection to naïve recipients. Thus, highly protective M-protein-specific MBCs may never develop following a single episode of pyoderma, contributing to the slow acquisition of immunity and to streptococcal endemicity in at-risk populations.

GAS skin infections pose a significant health problem in the tropics. They are highly prevalent in developing countries as well as amongst the Indigenous populations of developed countries. In at-risk impoverished communities the epidemiology of GAS infections is very dynamic, leading to very high rates of streptococcal-associated serious pathology including rheumatic heart disease, glomerulonephritis and invasive GAS disease. Immunity to GAS takes over 20 years to develop and this has been attributed to sequence diversity of the type-specific surface M-protein. There are more than 250 different strains of GAS and it known that antibodies to the amino-terminal segment of the M-protein can kill organisms in a strain-specific manner in vitro. In the present study, using four different strains of GAS isolated from the skin lesions of Aboriginal patients in the Northern Territory of Australia, we make the discovery that skin infection does not induce long-lived type-specific immunity. However, following reinfection with the same strain memory B cells are generated and long-term strain-protective immunity then develops. The dependence on reinfection for the development of strain-specific immunity compounds with antigenic diversity of the M-protein and provides a rational explanation for the very slow acquisition of streptococcal immunity.

Progress in VZV vaccination? Some concerns

Since 1995, many countries have been aiming to replace the natural immunity against varicella by a vaccine-induced immunity to protect against varicella and herpes zoster. While the frequency of varicella in childhood has been significantly reduced, in future, herpes zoster morbidity might increase in the elderly due to the weaker immunity post-vaccination and the absence of immunity boosting silent reinfections. In countries, where less than 90 % of children are covered by universal vaccination, varicella zoster virus (VZV) infection is not completely eradicated, but might move from childhood to the age of young adults who suffer from more serious complications. A special VZV vaccine against herpes zoster in adults aged >60 years has proven to be effective in many cases, but not all vaccinees. This might lead to problems regarding the acceptance of vaccination and delay rapid antiviral therapy to prevent the post-zosteric neuralgia. An efficacious-inactivated VZV vaccine to protect immunocompromised patients is still missing. VZV vaccines and vaccination strategies have to be optimised to avoid that the quality of life and cost savings from varicella reduction in childhood are offset by more VZV diseases in adults.

Assessment of mumps virus-specific antibodies by different serological assays: which test correlates best with mumps immunity?

Mumps is one of the vaccine-preventable childhood diseases and it has not yet been eradicated in Germany. This raises the question as to whether the available mumps vaccines are effective enough to prevent mumps and which antibody test system allows the authentic assigning of mumps-specific immunity. In an attempt to answer this question, we analysed 227 sera samples from medical students of the University Hospital Frankfurt/Main, Germany, using different test systems: indirect immune fluorescence, neutralisation assay, routine ELISA and newly developed immunoassays, which contain the mumps nucleoprotein and the wild-type strain Enders ATCC VR106, respectively. Mumps vaccination coverage of the screened collective amounted to 75.1%, which differs notably from the detected mumps-specific seropositivity rates in the literature (range 53.3% to 82.4%). In contrast, a small group of unvaccinated students had much higher seropositivity rates. Of course, assigned vaccination coverage and calculated seropositivity rates are not effective enough to interrupt the transmission of the mumps virus. The often-occurring mumps outbreaks, some in highly vaccinated populations, may not always demonstrate vaccine failure. The investigation of newly developed test systems and the occurrence of different mumps virus genotypes should also be considered.

Reliability of medical students' vaccination histories for immunisable diseases

BACKGROUND

Medical students come into contact with infectious diseases early on their career. Immunity against vaccine-preventable diseases is therefore vital for both medical students and the patients with whom they come into contact.

METHODS

The purpose of this study was to compare the medical history and serological status of selected vaccine-preventable diseases of medical students in Germany.

RESULTS

The overall correlation between self-reported medical history statements and serological findings among the 150 students studied was 86.7 %, 66.7 %, 78 % and 93.3 % for measles, mumps, rubella and varicella, conditional on sufficient immunity being achieved after one vaccination. Although 81.2 % of the students' medical history data correlated with serological findings, significant gaps in immunity were found.

CONCLUSION

Our findings indicate that medical history alone is not a reliable screening tool for immunity against the vaccine-preventable diseases studied.

Seroprevalence of vaccine preventable and blood transmissible viral infections (measles, mumps, rubella, polio, HBV, HCV and HIV) in medical students

In the course of clinical training medical students are in particular exposed to infectious diseases. Therefore, the present study was performed to investigate the immunity status of 223 medical students in their first clinical semester to job-related diseases. Specific serological antibody testing of hepatitis B-virus (HBV), hepatitis C-virus (HCV), human immunodeficiency virus (HIV), varicella zoster- (VZV), measles-, mumps-, rubella and polioviruses' type 1, 2 and 3 were performed. The results yielded, that 69.5% of the students had an anti-HBs-level > or =10 IU/l and 54.7% > or =100 IU/l. Neither HCV infection nor HIV infection were found, but one student showed an active HBV infection. Virus specific immunity rates were found in 91.5% for measles, 80.3% for mumps, 90.1% for rubella and 96.9% for varicella. Furthermore the medical students demonstrated neutralizing antibodies to polioviruses: 95.1% (type 1), 96.9% (type 2) and 70% (type 3). 68.2% had antibodies (titer 1:> or =10) against all three virus types. The partly significant gaps of immunity in the students need to be closed prior to the first contact with patients.