Current vaccination policies may not be sufficient to achieve and maintain measles elimination and prevent future resurgence in Australia, Ireland, Italy, the UK and the US, according to a study published in the open access journal BMC Medicine.
To successfully achieve and maintain measles elimination in these countries in the medium to long term, further country-specific immunisation efforts may be needed in addition to current strategies.
Measles elimination has been defined as the absence of endemic measles transmission in a region or other defined geographic area for twelve months or longer.
A team of researchers at the Bruno Kessler Foundation and Bocconi University, Italy used a computer model to simulate the evolution of measles immunity between 2018 and 2050 in seven countries; Australia, Ireland, Italy, Singapore, South Korea, the UK and the US.
The authors focused their analysis on countries with a routine two-dose measles vaccination programme and a high primary school involvement rate, but with different demographics and vaccination histories.
The aim was to evaluate the effect of possible adjustments to existing immunization strategies and to estimate the proportion of people who may remain susceptible to measles in high-income countries over time.
What is measles?
Measles is the most contagious of all infectious diseases.
In certain cases, complications with the disease may even be serious and life threatening.
A very high vaccination rate of the population is a prerequisite to prevent the spreading of measles. Low rates of vaccination may lead to the outbreak of the disease.
That is the main cause for outbreaks in Europe and other places all over the world.
Even in measles-free countries, such as in Israel, there still is a high risk of infection and spread of measles by foreign patients.
Unvaccinated individuals exposed to a measles patient has a higher than a 90% chance of being infected!
The safest and most effective way to prevent measles and its complications is by getting vaccinated against the disease.
Cause
Measles is caused by the measles virus, which belojgs to the Paramyxovirus family.
Ways of getting infected with measles
Measles is transmitted from one person to another if the virus is ejected to the environment by coughing, sneezing, or having direct contact with nose secretions and phlegm.
Infection can also occur from staying in a room with a patient, up to two hours after the patient left the room.
Symptoms
The symptoms will usually appear 10 to 14 days post virus exposure.
The first symptioms are high fever, a runny nose, cough, red eyes and light sensitivity.
On the fourth or fifth day, a dark red rash appears on the skin. Usually the rash starts with the neck and gradually spreads toward the face, body and limbs. A
t first, there are many spread spots and they tend to form a rash that covers extensive parts of the body.
The rash begins to fade on the third day of its appearance and this is usually accompanied by an improvement in the patient’s comfort.
The rash is similar to the small and condensed flowers of the sea squill (Hatzav), hence the name of the disease in Hebrew.
Possible complications
Measles may cause severe complications to the respiratory system and the nervous system.
Approximately a third of the patients will develop complications such as middle ear infection, diarrhea and cornea infection.
Rare complications include pneumonia and encephalitis.
A highly rare complication (about one to four cases out of one million) which can appear several years after the measles episode is a degenerative disease of the brain which causes a serious and irreversible damage to the central nervous system, including mental deterioration and convulsions.
The risk for complications is higher among children under five years of age, among adults over 20 years of age and in patients with compromised immune systems.
One out of a thousand children infected with measles may die.
Prevention
The safest and effective way to prevent infection is by getting vaccinated against the disease on schedule.
The vaccine is safe.
The vaccination efficacy in the prevention of measles is extremely high (approximately 97% after getting two vaccine doses).
Few individuals vaccinated yet are susceptible to the disease are expected to experience mild symptoms in comparison to unvaccinated individuals.
The vaccine provides protection two weeks after getting the vaccine and immunization persists dozens of years afterwards.
The measles vaccine is comprised of an attenuated virus subcutaneously injected; it is a combined MMR/MMRV serum against measles, mumps, rubella, and varicella.
In Israel, it is not possible to get vaccinated solely against the measles virus.
The vaccination is sceduled:
- At 12 months of age
- At first grade
Exposure to measles
In a unvaccinated individual exposed to measles, post exposure vaccination may prevent or relieve the severity of the disease.
- Active vaccine– delivered within 72 hours post exposure
- Passive vaccine – (Immunoglobulin) – delivered within six days post exposure to individuals who cannot receive the active vaccine and/or are at a high risk for the disease.
The Ministry of Health epidemiologic team is responsible for finding individuals who have been exposed to measles and for deciding which serum to vaccinate them with.
In case of exposure to a measles patient, and the development of symptoms such as fever or rash, the family physician should be contacted in order for the clinic to prepare, so that other patients will not be exposed to the virus. Moreover, as soon as a patient arrives at emergency services, staff must be informed.
Measles in Israel
During the 1950’s thousands of measles patients have been reported in Israel every year.
Since the introduction of the vaccine in 1967 a continuous decrease in the number of patients has taken place, yet outbreaks of the disease still occur, mostly amongst populations that do not vaccinate their children and as a result of bringing the disease from abroad.
Following the country’s high vaccination coverage rate, incidences of measles are expected mainly among unvaccinated individuals.
However, patients infected abroad can facilitate the outbreak of the disease, in spite of the high vaccination coverage.
A small number of tourists and travellers had brought the disease to Israel, which later spread among unvaccinated population, between March 2018 and end of April 2019 more than 4100 individuals contracted measles.
Measles worldwide
In some European countries and in India, recurring measles outbreaks have been reported.
More than 75% of all reported cases in 2017 were recorded in the first half of the year, with the highest numbers in the months of March (2 802), April (2 474) and May (2 244). Following a sharp decline in the number of cases in the summer months, a steady increase was observed towards the end of the year (Figure 1).
The number of cases by country and the subnational notification rate per million population per country for the calendar year 2017 are presented in Figures 2 (left panel) and 3 respectively.
For January 2018, the number of cases (n=1 073) by country is presented in Figure 2 (right panel). All but one (Malta) EU/EEA country reported measles cases in 2017 and January 2018.
In 2017, most cases were reported by Romania (5 608), Italy (5 098), Greece (967), Germany (929) and France (518), accounting for, respectively 38%, 35%, 7%, 6% and 4% of all cases reported by EU/EEA countries. Since the end of 2017, Greece and France have reported a notable increase in cases.
In 2017, 37 deaths due to measles were reported across the EU/EEA; with 26 in Romania, four in Italy, two in Greece, and one each in Bulgaria, France, Germany, Portugal and Spain [3] (Figure 4). A further seven deaths have been reported in 2018; three in Romania, two in Italy, and one each in Greece and France [4].
In 2017, among 13 716 cases with known importation status, 12 160 (89%) were reported to be endemic, 1 173 (9%) import-related and 383 (3%) imported.
Of 14 600 cases with known age, 5 284 (37%) were in children less than five years of age, while 6 656 (45%) were aged 15 years or older.
The highest incidence was reported in children below one year of age (365.9 cases per million), followed by children from 1 to 4 years of age (164.4 cases per million).
Among 13 753 cases with known vaccination status, 87% were unvaccinated, 8% were vaccinated with one dose of measles-containing vaccine, 3% were vaccinated with two or more doses, and 2% were vaccinated with an unknown number of doses. Of all cases, 6% had an unknown vaccination status.
The proportion of cases with unknown vaccination status was highest in adults aged 25–29 years (13%).
The proportion of unvaccinated cases among the age groups targeted for vaccination ranged from 72% (25–29 year olds) to 86% (1–4 year olds).
Among cases below one year of age, the proportion of unvaccinated cases was 96% as most vaccination programmes only target vaccination from one year of age.
Infants below the age of one year are particularly vulnerable to complications from measles and are best protected by herd immunity. Herd immunity is achieved when population coverage for the second dose of a measles-containing vaccine is at least 95%.
Measles continues to spread across Europe as the vaccination coverage in many EU/EEA countries is suboptimal.
The latest available data on national vaccination coverage for the first and second doses of measles-containing vaccine are presented in Figure 5 [5].
The vaccination coverage in 2016 for the second dose of measles-containing vaccine was below 95% in 22 of 29 EU/EEA countries with data (Figure 5).
If the elimination goal is to be reached, vaccination coverage needs to increase in a number of countries as, operationally, the vaccination coverage target for the second dose has to be at least 95% to interrupt measles circulation.
The authors’ projections up until 2050 suggest that if current vaccination policies remain unchanged, the proportion of the population susceptible to measles would only remain below 7.5% in Singapore and South Korea, two countries which had high vaccination coverage in the past.
Previous research estimated that the proportion of the population that does not have immunity (maximum susceptibility) needs to be 7.5% or less for measles to be eliminated.
In 2018, the proportion of the population susceptible to measles infection in the countries under study ranged from 3.7% in the UK to 9.3% in Italy (the only country where the proportion was found to be higher than 7.5%).
In Australia, Ireland, the UK and the US, vaccination from routine programmes would need to continuously cover more than 95% of the population to keep the proportion of susceptible individuals below 7.5% until 2050.
Dr. Filippo Trentini, the first author said: “In recent years, we’ve witnessed a resurgence of measles cases even in countries where, according to World Health Organisation guidelines, elimination should already have been achieved.
This resurgence is due to suboptimal vaccination coverage levels.
In Italy, where measles incidents rates were among the highest, the government has made measles vaccination compulsory for children before they enter primary school.
We investigated the potential of this and other policies to reinforce immunisation rates in seven high-income countries.”
Measles elimination has been defined as the absence of endemic measles transmission in a region or other defined geographic area for twelve months or longer.
Co-author Dr. Stefano Merler added: “Our results suggest that most of the countries we have studied would strongly benefit from the introduction of compulsory vaccination at school entry in addition to current immunisation programmes.
In particular, we found that this strategy would allow the UK, Ireland and the US to reach stable herd immunity levels in the next decades, which means that a sufficiently high proportion of individuals are immune to the disease to avoid future outbreaks.
To be effective, mandatory vaccination at school entry would need to cover more than 40% of the population.”
In Italy, the fraction of susceptible individuals by 2050 is projected to be 10%, even if coverage for routine vaccination reaches 100%, and additional vaccination strategies targeting both children at school entry and adults may be needed to achieve elimination.ABOUT THIS NEUROSCIENCE RESEARCH ARTICLE
Source:
Biomed Central
Media Contacts:
Anne Korn – Biomed Central
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The image is in the public domain.
Original Research: Open access
“The introduction of ‘No jab, No school’ policy and the refinement of measles immunisation strategies in high-income countries”. Filippo Trentini, Piero Poletti, Alessia Melegaro and Stefano Merler.
BMC Medicine. doi:10.1186/s12916-019-1318-5
