No Jab, No School Policy: An effective Way to Contain Measles in Western Countries
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No Jab, No School Policy: An effective Way to Contain Measles in Western Countries

AN ANALYSIS BY ALESSIA MELEGARO AND COLLEAGUES CONCLUDES THAT ROUTINE VACCINATION PROGRAMS ARE NOT ENOUGH TO PRESERVE HERD IMMUNITY IN AUSTRALIA, IRELAND, ITALY, THE UK, AND THE US. IN ITALY, EVEN THE MANDATORY JAB AT SCHOOL ENTRY WOULD NOT BE SUFFICIENT

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 immunization 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.
 
Alessia Melegaro, Associate Professor of Demography and Epidemiology at Bocconi University, and a group of researchers from Fondazione Bruno Kessler 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 program 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. 
 
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 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 programs would need to continuously cover more than 95% of the population to keep the proportion of susceptible individuals below 7.5% until 2050. 
 
«The trigger for our analysis was the interest in evaluating the potential impact of the policy introduced in Italy, which is based on mandatory vaccination», Prof. Melegaro said. «We concluded that, by assuming fully compliance to the recently approved regulation (i.e.100% coverage), vaccination at school entry would determine acceptable levels of susceptibility, resulting in around 9% of susceptible in 2050 instead of the 15% of susceptibility expected by relying on routine programs only. However, our simulations highlight that the interruption of measles circulation and the achievement of measles elimination in settings similar to the Italian one would also require further efforts to reduce susceptibility in older age groups, due to immunity gaps in adults caused by past sub-optimal coverage»,
 
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 Organization guidelines, elimination should already have been achieved. This resurgence is due to suboptimal vaccination coverage levels».
 
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 immunization programs. 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».

Filippo Trentini, Piero Poletti, Alessia Melegaro, Stefano Merler, The introduction of ‘No jab, No school’ policy and the refinement of measles immunisation strategies in high-income countries, in BMC Medicine 2019 17:86, doi: 10.1186/s12916-019-1318-5.
 

by Ezio Renda

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