Twice vaccinated recipients are better protected against epidemic measles than are single dose recipients of measles containing vaccine

A guide to vaccinology: from basic principles to new developments

Immunization is a cornerstone of public health policy and is demonstrably highly cost-effective when used to protect child health. Although it could be argued that immunology has not thus far contributed much to vaccine development, in that most of the vaccines we use today were developed and tested empirically, it is clear that there are major challenges ahead to develop new vaccines for difficult-to-target pathogens, for which we urgently need a better understanding of protective immunity. Moreover, recognition of the huge potential and challenges for vaccines to control disease outbreaks and protect the older population, together with the availability of an array of new technologies, make it the perfect time for immunologists to be involved in designing the next generation of powerful immunogens. This Review provides an introductory overview of vaccines, immunization and related issues and thereby aims to inform a broad scientific audience about the underlying immunological concepts.

This Review, aimed at a broad scientific audience, provides an introductory guide to the history, development and immunological basis of vaccines, immunization and related issues to provide insight into the challenges facing immunologists who are designing the next generation of vaccines.

Effect of age at vaccination on the measles vaccine effectiveness and immunogenicity: systematic review and meta-analysis

Background

The objectives of this review were to evaluate the effect of age at administration of the first dose of a measles-containing vaccine (MCV1) on protection against measles and on antibody response after one- and two-dose measles vaccinations.

Methods

We conducted a systematic review of the PubMed/MEDLINE, Embase, Web of Science and Cochrane databases (1964–2017) to identify observational studies estimating vaccine effectiveness and/or measles attack rates by age at first vaccination as well as experimental studies comparing seroconversion by age at first vaccination. Random effect models were used to pool measles risk ratios (RR), measles odds ratios (OR) and seroconversion RR of MCV1 administered at < 9, 9–11 or ≥ 15 months compared with 12 or 12–14 months of age.

Results

We included 41 and 67 studies in the measles protection and immunogenicity analyses. Older age at MCV1, from 6 to ≥15 months, improved antibody response and measles protection among one-dose recipients. Pooled measles RR ranged from 3.56 (95%CI: 1.28, 9.88) for MCV1 at < 9 months to 0.48 (95%CI: 0.36, 0.63) for MCV1 at ≥15 months, both compared to 12–14 months. Pooled seroconversion RR ranged from 0.93 (95%CI: 0.90, 0.96) for MCV1 at 9–11 months to 1.03 (95%CI: 1.00, 1.06) for MCV1 at ≥15 months, both compared to 12 months. After a second dose, serological studies reported high seropositivity regardless of age at administration of MCV1 while epidemiological data based on few studies suggested lower protection with earlier age at MCV1.

Conclusions

Earlier age at MCV1 decreases measles protection and immunogenicity after one dose and might still have an impact on vaccine failures after two doses of measles vaccine. While two-dose vaccination coverage is most critical to interrupt measles transmission, older age at first vaccination may be necessary to keep the high level of population immunity needed to maintain it.

Reduced Antibody Response to Infant Measles Vaccination: Effects Based on Type and Timing of the First Vaccine Dose Persist After the Second Dose

Background

The effect of age at first dose on the immunogenicity of a 2-dose pediatric schedule of measles-mumps-rubella (MMR) or measles-mumps-rubella-varicella (MMRV) vaccine was assessed in children born to mostly vaccinated mothers.

Methods

Immunogenicity data among children given their first measles vaccine dose between 11 and 22 months of age were pooled from 5 randomized controlled trials conducted in Europe and the United States between 2004 and 2010. Measles antibody titers were measured by enzyme-linked immunosorbent assay before and after each dose; geometric mean concentrations (GMCs) and the proportion seronegative (GMC <150 mIU/mL) were derived by age at first dose.

Results

Among 5542 children given a first measles vaccine dose at 11, 12, 13-14, and 15-22 months of age, the proportion seronegative decreased from 8.5% to 3.2%, 2.4%, and 1.5%, respectively (P < .001), whereas GMCs increased with older age measles vaccine initiation (P < .001). MMRV induced higher GMCs than MMR (P < .001). First and second dose GMCs were highly correlated (Spearman coefficient = 0.8).

Conclusions

As previously noted among infants born to mothers with history of wild-type measles, antibody responses among children born to vaccinated mothers were reduced based on earlier administration of their first measles vaccine dose at ≤12 vs ≥15 months of age. Negative effects of earlier age at first measles vaccine dose persisted after the second dose. The measles elimination goal may require a careful balance between earlier infant protection and the risk of reduced antibody responses and secondary vaccine failure among successive birth cohorts systematically initiated to measles vaccination <15 months of age.

Persistence of measles antibodies, following changes in the recommended age for the second dose of MMR-vaccine in Portugal

In populations vaccinated with two doses of combined measles-mumps-rubella vaccine (MMR), the serum levels of antibodies against measles depend on the vaccination schedule, time elapsed from the last dose and the area-specific epidemiological situation. Variables measuring "schedule" are age at first and second doses of MMR and intervals derived from that. Changes in vaccination schedules have been made in Portugal. The specific objectives of this study were to measure the association between those potential determinants and the concentration of measles-specific IgG antibodies, after the second dose of MMR. Convenience samples of three Portuguese birth cohorts were selected for this study (41, 66 and 60 born, respectively, in 2001-2003, 1990-1993 and 1994-1995). Geometric mean concentrations (GMC) for measles IgG were, respectively, 934, 251 and 144mIU/ml; p<0.001). Anti-measles-IgG serum concentration decreased with time since last vaccination (waning immunity) and was not influenced by any other component of vaccination schedule, namely age at vaccination with the second dose of MMR. Waning levels of measles antibodies have been observed elsewhere but not as fast as it was observed in Portuguese birth cohorts in this study. Changes in the vaccination schedules might have to be considered in the future.

[Re-emergence of measles in the province of Guadalajara, Spain. Is it time to establish new strategies for its elimination?]

BACKGROUND

Measles is a viral infection that was almost eradicated, but it is re-emerging in Spain and Europe in recent years. The aim of this study was to describe the microbiological, clinical and epidemiological characteristics of a measles outbreak that occurred in Guadalajara (Spain) from June to August 2012.

METHODS

A descriptive and retrospective study was conducted. A total of 117 samples (including serum, urine and pharyngeal swabs) from 52 patients were analyzed for measles.

RESULTS

Measles was diagnosed in 50 patients, 41 of them by microbiological diagnosis, and 9 by epidemiological link. The patients were grouped in four community outbreaks. No imported cases were observed. Positive IgM and positive CRP were detected in 25 patients, positive CRP only in 11 and positive IgM only in 5. The genotype D4 was identified in 13 patients and the genotype A in a post-vaccine case. The age groups most affected were adults between 20-34 years of age (38%) and younger than 15 months (26%). The large majority (86%) of patients were unvaccinated (44% Roma population, 27% younger than 15 months, 11% ideological reasons), 6% had one vaccine dose. The signs/symptoms were: rash and fever, 100%, cough, 82%, and conjunctivitis 50%. Almost one-third (32%) of patients were hospitalized, and 28% had complications.

CONCLUSIONS

It is very important to intensify the epidemiological surveillance of infections in the elimination phase. The increased incidence of measles was associated to unvaccinated pockets, presenting a challenge for Public Health Centers. These agencies should prepare strategies to obtain a higher vaccine coverage for the eradication of measles.

Immune response to 1 and 2 dose regimens of measles vaccine in Pakistani children

Measles is a significant problem in Pakistan despite vaccine coverage rates reported at 80%. The purpose of this study was to determine the serologic response in children after one dose of measles vaccine at 9 mo versus two doses at 9 and 15 mo of age. From March through December 2006, children were enrolled from immunization clinics and squatter settlements in Karachi. Blood samples were taken from children in Group A at 9-10 mo of age prior to measles vaccine and 8 to 11 weeks later; from children in Group B at 16-17 mo of age after receiving 2 doses of measles vaccine; and from children in Group C who had received at least one dose of measles vaccine by 5 y of age. After the first dose of measles vaccine, 107/147 (73%) of children in Group A were seropositive, 157/180 (87%) of children in Group B were seropositive after two doses and 126/200 (63%) of children in Group C were seropositive at 5 y of age. The post-vaccination geometric mean antibody concentrations were higher in females than males in groups A (irrespective of pre-vaccination antibody levels) and B. The serologic response to one and two doses of measles vaccine was lower in children in Karachi than has been reported in many other countries. Two doses of vaccine were significantly better than one dose. An in-depth investigation is needed to determine the reason for the lower-than-expected protection rates. Differences in immunogenicity between genders need to be further studied. Recent introduction of supplemental measles vaccine doses should help control measles in Pakistan.

MMR vaccination and disease elimination: the Finnish experience

Measles, mumps and rubella (MMR) vaccinations have been included in Finland's national vaccination program as a two-dose schedule since 1982. Owing to the high (>95%) coverage of vaccinations, indigenous MMR diseases were eliminated from Finland by the mid-1990s. In 1982, the incidence of measles, mumps and rubella was 105, 43 and 64 per 100,000 population, respectively, but declined to 0.1 per 100,000 population for all MMR diseases in 1995. Since then, the few cases of measles, mumps and rubella imported annually have not caused any outbreaks. Several research projects that started along with the vaccination campaign have provided important support throughout the program. The vaccine was proven to be safe, immunogenic and effective. Antibody follow-up has revealed that MMR vaccine-induced antibodies wane over time, and concerns have arisen about the continuation of this good situation. High vaccination coverage, enhanced surveillance and preparedness to administer additional doses when needed are key factors for future success. Here we present an overview of MMR vaccinations and the Finnish experience of the MMR disease elimination process, and we describe surveillance activities in the era following elimination in Finland.

Measles, mumps, and rubella in Finland: 25 years of a nationwide elimination programme

A nationwide programme to eliminate indigenous measles, mumps, and rubella, mainly by vaccinating children twice, was launched in Finland in 1982. Strong scientific methods to examine the immunological, clinical, and epidemiological variables have accompanied the programme. Measles was eliminated in 1996, and mumps and rubella in 1997. Now, 25 years from the start of this programme, Finland is facing new challenges. Since elimination, eight, 32, and six cases of measles, mumps, and rubella, respectively, have been reported. Of those, seven cases were failures of mumps vaccinations and one case was a rubella vaccination failure. Although outbreaks have been averted, the risks are increasing because the unvaccinated population is growing, epidemics occur in nearby countries, breakthrough cases arise, and declining antibodies suggest waning immunity. The chances for natural boosters are now at a minimum, and individuals are increasingly protected solely by vaccination. To maintain the absence of these diseases, the adopted policy should continue, but the country should also be prepared for prompt supplementary vaccinations in the case of epidemic outbreaks.

Long-term persistence of antibodies after one or two doses of MMR-vaccine

Outbreaks of measles, mumps and rubella have occurred recently despite long-standing mass immunization with MMR. Antibody titres for measles, mumps and rubella of 160 students (17-23 years) with proof of at least one MMR-vaccine were studied according to the number of MMR-vaccines received. The proportion of subjects with positive antibody titres was significantly higher in those who received two vaccines against measles (77.1% versus 58.7%, p=0.05), mumps (67.5% versus 55.6%, p=0.009) and rubella (99.2% versus 71.4%, p=0.008). Comparable significant trends were seen for GMTs for measles and mumps. A similar non-significant trend was noted for rubella.

Human leukocyte antigen and interleukin 2, 10 and 12p40 cytokine responses to measles: is there evidence of the HLA effect?

HLA class I and class II associations were examined in relation to measles virus-specific cytokine responses in 339 healthy children who had received two doses of live attenuated measles vaccine. Multivariate linear regression modeling analysis revealed suggestions of associations between the expression of DPA1*0201 (p=0.03) and DPA1*0202 (p=0.09) alleles and interleukin-2 (IL-2) cytokine production (global p-value 0.06). Importantly, cytokine production and DQB1 allele associations (global p-value 0.04) revealed that the alleles with the strongest association with IL-10 secretion were DQB1*0302 (p=0.02), DQB1*0303 (p=0.07) and DQB1*0502 (p=0.06). Measles-specific IL-10 secretion associations approached significance with DRB1 and DQA1 loci (both global p-values 0.08). Specifically, suggestive associations were found between DRB1*0701 (p=0.07), DRB1*1103 (p=0.06), DRB1*1302 (p=0.08), DRB1*1303 (p=0.06), DQA1*0101 (p=0.08), and DQA1*0201 (p=0.04) alleles and measles-induced IL-10 secretion. Further, suggestive association was observed between specific DQA1*0505 (p=0.002) alleles and measles-specific IL-12p40 secretion (global p-value 0.09) indicating that cytokine responses to measles antigens are predominantly influenced by HLA class II genes. We found no associations between any of the alleles of HLA A, B, and Cw loci and cytokine secretion. These novel findings suggest that HLA class II genes may influence the level of cytokine production in the adaptive immune responses to measles vaccine.

Identification of primary and secondary measles vaccine failures by measurement of immunoglobulin G avidity in measles cases during the 1997 São Paulo epidemic

Despite almost universal use of measles vaccines in recent decades, epidemics of the disease continue to occur. Understanding the role of primary vaccine failure (failure to seroconvert after vaccination) and secondary vaccine failures (waning immunity after seroconversion) in measles epidemics is important for the evaluation of measles control programs in developing countries. After a measles epidemic in São Paulo, Brazil, 159 cases previously confirmed by detection of specific immunoglobulin M (IgM) antibodies were tested for IgG avidity, and a secondary immune response, defined by an IgG avidity index of at least 30%, was established in 30 of 159 (18.9%) patients. Among the 159 patients, 107 (67.3%) had not been vaccinated and 52 (32.7%) had received one or more doses of measles vaccine. Of the 107 unvaccinated patients, 104 (97.2%) showed a primary immune response, defined as an IgG avidity index of less than 30%. Among the 52 patients with documented vaccination, 25 (48.1%) showed a primary immune response and 27 (51.9%) showed a secondary immune response, thereby constituting a secondary vaccine failure. Primary vaccine failure was observed in 13 of 13 patients vaccinated prior to 1 year of age and in 43.5 and 12.5%, respectively, of patients receiving one or two doses after their first birthdays. These results provide evidence that measurement of IgG avidity can be used to distinguish between primary and secondary vaccine failures in vaccinated patients with measles; the method can also be a useful tool for the evaluation of measles control programs.

Immunity to measles in the Croatian population

In the frame of measles elimination activities, sera from 1205 Croatian citizens from all parts of the country and of all ages were tested, using Gull Laboratories ELISA, for measles IgG. Equivocal results were found in 50 subjects. Of the remaining 1155 participants, 118 or 10.2% were negative and 1037 or 89.8% positive. The proportion of seronegatives ranged from zero (age groups 41-50, 51 and more) up to 21.4% (1 year of age). As for their distribution into age groups suggested by the European Regional Office of WHO, there were 12.7, 8.9, 9.5 and 8.8% negatives in age groups 1-4, 5-9, 10-14 and 15 + years, respectively. According to these results, only the first two age groups meet WHO criteria, indicating that vaccination coverage higher than the reported 90-94% should be attained if one is to expect measles elimination.

Fully vaccinated children are rare: immunization coverage and seroprevalence in Austrian school children

Vaccination coverage for vaccine-preventable diseases in Austria as well as in many Central European countries has been reported to be too low to eradicate such diseases and prevent further outbreaks. Austria lacks an adequate surveillance system to monitor prevalence of the diseases, the vaccination coverage and seroconversion. School children aged 10-14 years (n = 1077) were recruited in all four schools in the city of Schwaz, Austria, to present their vaccination documents and to give blood for serological testing (diphtheria, pertussis, measles, mumps, rubella, varicella). All participants received a report with a personal guideline for (re-) vaccination. Overall vaccination coverage was 86.4% for measles, 85.5% for mumps and 35.0% for rubella. Tetanus vaccination coverage was 98.4% for the first, 97.8% for the second and 96.7% for the third dose, while 55.4% of the study subjects received the recommended two booster injections. For diphtheria the corresponding vaccination coverage was found to be almost identical. Pertussis coverage was lower in general (first dose: 90.9%; second dose: 89.0%; third dose: 86.5%). Oral poliomyelitis vaccination showed a coverage of 98.6, 96.5, 95.3%, with 78.7% receiving the fourth dose. Overall 38.7% were classified as fully vaccinated. Seropositivity for measles was found in 90.4%, for mumps in 61.8%, for rubella in 82.3%, for diphtheria in 65.8%, for pertussis in 35.6% and for varicella in 95.0%. In summary, fully vaccinated children are rare and intensive public health efforts will be necessary to reach higher levels of immunity and prevent further outbreaks.

Seroconversion after measles vaccination at nine and fifteen months of age

BACKGROUND

Despite high vaccination coverage, single dose measles immunization programs have been unsuccessful in eliminating the disease. Because seroconversion rates are lower in infants vaccinated before 12 months of age, a second dose of measles vaccine is recommended at 15 months. The aim of this study was to determine the seroconversion rates in children after the first and second doses of measles vaccinations at 9 and 15 months of age.

METHODS

Study population comprised 116 infants attending the Well Baby Clinic of Istanbul University, Faculty of Medicine. Serum specimens were obtained from children before and 1 month after the first measles (Rouvax, Schwarz strain 1000 TCID(50)) vaccine given at 9 months. A second dose was given to 72 children at 15 months of age as measles-mumps-rubella (Trimovax, Schwarz measles strain, 1000 TCID(50); Urabe Am 9 mumps strain, 5000 TCID(50); Wister RA 27/3 rubella strain, 1000 TCID(50)). Third blood samples were collected 20 months after the second vaccine.

RESULTS

Passive antibody positivity rate was 5.2% at the age of 9 months. Seroconversion rate was 77.6% after the first dose and 81.9% after the second dose of measles vaccine. Of 15 children who were seronegative, 13 (86.7%) became seropositive after the immunization at 15 months. Eleven children (19.2%) seroconverted from positive to negative after the second vaccine.

CONCLUSION

The two dose schedule seems to increase the seropositivity rate. Our findings also indicate that increasing vaccination coverage and revaccination at 6 years of age are important even with the early two dose schedule.

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.

The challenge of improving the efficacy of measles vaccine

Despite a safe and effective measles vaccine, measles still claims an estimated 800,000 lives per year mostly among children in developing countries. This paper deals with strategies to improve vaccine efficacy and prevent unnecessary deaths, including considerations of one dose at 9 months strategy for developing countries, strain of vaccine, potency and number of doses of measles vaccine. After more than 20 years of measles immunisation in the developing world, the epidemiology of measles is radically changed, and the absence of measles epidemics might lead to waning immunity due to less clinical and subclinical infections boosting the antibody level. An increasing proportion of mothers are vaccinated, thus transferring a lower maternal antibody level to their infants who will be susceptible to measles at a younger age. The strategies to limit nosocomial measles infection and spread of measles epidemics are reviewed. Though the measles elimination programmes have been very effective in the Americas, it seems unlikely that they will be equally effective in the rest of the world. Even if eradication should be possible, it might be unwise to stop measles vaccination because the vaccine apparently has beneficial effects and because it would make measles a likely weapon for bio-terrorism. If we are unlikely to get rid of measles and measles vaccine, it might be wise to study further some of the many unanswered questions regarding the long-term effects of measles and measles vaccination.

Clinical and serological studies on CAM-70 live attenuated measles vaccine: an 18-year survey at a pediatric clinic in Japan

Live attenuated measles vaccine chorioallantonic membrane-70 (CAM-70) was administered to 471 healthy individuals over an 18-year period (1982-1999) at the pediatric clinic of Showa Hospital in Japan. Seroconversion occurred in 95.4% (418/438) of initially seronegative subjects. Reactions to the vaccine were generally insignificant, except for vaccine-related fever in about 20%. In February 2000, we made a questionnaire survey of 272 initially seronegative subjects who were vaccinated, from 0.7 to 18.1 years (mean: 5.5 years) earlier. Six (2.2%) of them contracted breakthrough measles during follow-up. The vaccine was generally safe and effective. However, it warrants investigation that the incidence of breakthrough measles may increase in the future in Japan.

Immunogenicity of second dose measles-mumps-rubella (MMR) vaccine and implications for serosurveillance

Measles and mumps, but not rubella, outbreaks have been reported amongst populations highly vaccinated with a single dose of measles-mumps-rubella (MMR) vaccine. Repeated experience has shown that a two-dose regime of measles vaccine is required to eliminate measles. This paper reports the effect of the first and second MMR doses on specific antibody levels in a variety of populations.2-4 years after receiving a first dose of MMR vaccine at age 12-18 months, it was found that a large proportion of pre-school children had measles (19.5%) and mumps (23.4%) IgG antibody below the putative level of protection. Only a small proportion (4.6%) had rubella antibody below the putative protective level. A total of 41% had negative or equivocal levels to one or more antigens. The proportion measles antibody negative (but not rubella or mumps) was significantly higher in children vaccinated at 12 months of age than at 13-17 months. There was no evidence for correlation of seropositivity to each antigen, other than that produced by a small excess of children (1%) negative to all three antigens. After a second dose of MMR, the proportion negative to one or more antigens dropped to <4%. Examination of national serosurveillance data, found that following an MR vaccine campaign in cohorts that previously received MMR, both measles and rubella antibody levels were initially boosted but declined to pre-vaccination levels within 3 years. Our study supports the policy of administering a second dose of MMR vaccine to all children. However, continued monitoring of long-term population protection will be required and this study suggests that in highly vaccinated populations, total measles (and rubella) IgG antibody levels may not be an accurate reflection of protection. Further studies including qualitative measures, such as avidity, in different populations are merited and may contribute to the understanding of MMR population protection.

Day-to-day reactogenicity and the healthy vaccinee effect of measles-mumps-rubella vaccination

OBJECTIVE

Revaccination policies adopted in many countries to control measles have raised various safety issues including those concerning the second vaccine dose. We performed a prospective, double-blind, crossover trial among twins receiving a measles-mumps-rubella (MMR) vaccine.

STUDY DESIGN

The study comprised 1162 monozygous and heterozygous twins, each of whom randomly received placebo and then vaccine, or vice versa, 3 weeks apart, at 14 to 83 months of age. Most of the oldest children had previously been vaccinated against measles, and one half of the remainder of children had had the disease. Symptoms and signs were recorded daily on structured forms. Statistical methods included a complex analysis of the vaccine attributability of the symptoms and conditional logistic regression.

RESULTS

Vaccination-attributable events occurred in 6% overall. At 14 to 18 months of age, reactions developed between days 6 and 14, peaking at day 10. The clearest vaccine-attributable effect was fever exceeding 101.3 degrees F (38. 5 degrees C; odds ratio: 3.28; 95% confidence interval: 2.23-4.82; P <.001), but the same trend was found for rash, arthralgia, conjunctivitis, staying in bed, drowsiness, and irritability. At 6 years of age, systemic reactions occurred 5 to 15 times less frequently, only arthralgia being associated with vaccination. Zygocity, gender, history of allergy, or infections did not modify reactions. Instead, respiratory symptoms developed within days postinjection to a level of 15% to 20% without subsequent decline and with no difference between vaccinees and placebo recipients.

CONCLUSION

Vaccination was avoided during infections, but many small children became mildly ill within a week or so with no relation to vaccination (the healthy vaccinee effect). MMR vaccine was virtually nonreactogenic when given at 6 years of age. vaccine, measles, mumps, rubella, reactogenicity, adverse events, zygocity, healthy vaccinee effect.