Reacción a "Reactions: Spain detects first measles outbreaks since pandemic"

From different sources, there have been warnings of a resurgence of measles in recent months. This is happening in Europe, particularly in the United Kingdom, where 650 cases have been confirmed from October 1, 2023, to the end of February 2024, with 183 new cases in February alone.

It is logical to observe the same phenomenon in Spain, given the extraordinary contagiousness of measles and the very high mobility and interconnections of populations in Europe. In 2020, with the emergence of the pandemic, measles cases decreased to almost disappear (see image here, where it is observed that new cases ceased from March of that year), they remained at very low levels from 2021 to 2023. And now, in these first weeks of 2024, an increase in cases is beginning to be noticed.

The figures observed in Spain are still moderate, but they will surely increase, as in other countries.

In Spain, two circumstances should be considered:

• The favorable circumstance is that vaccination coverage is generally good, although improvable (see here). Speaking of coverage with two doses, it globally reaches 93.9%, below the target (95%), with Andalusia, Aragon, Asturias, Cantabria, Valencian Community, Murcia, and Navarra above the mentioned target. And below 90% (high risk) are: Castilla-La Mancha, Basque Country, La Rioja, Ceuta, and Melilla (Canary Islands and Extremadura only a few tenths above this figure). The Basque Country's figure of only 88% is extraordinarily worrying. Meanwhile, the Balearic Islands do not provide data (?).
• These coverage figures - good, but not so much - have at least two weaknesses, moreover: one, the delay in the registration of vaccination compliance, generally 1-2 years, so it is showing us an already "old" reality, a picture from 1-2 years ago, and we do not know the current reality; and two, the figures with geographical reference of autonomous community cover up the possible (real, according to numerous studies) variability of coverage in smaller areas and collectives, that is, it does not reveal the existing pockets of under-vaccination.

Finally, it is also relevant to mention that measles diagnoses could be escaping. That is to say, there may be more cases than those identified. The ISCIII report of 2022 states that, in our environment, the quality indicators of measles surveillance are not good in some of them: in 2022, the proposed objectives were achieved with the exception of the discarded cases rate; the target proposed by the WHO-Europe is ≥2 per 100,000 inhabitants, and the result achieved in Spain in 2022 has been only 0.4 discarded cases per 100,000 inhabitants (ISCIII Report, 2022). As this same report indicates, the sensitivity of the system for identifying and reporting suspected cases (basically the responsibility of the clinical services of the NHS) is failing, while the subsequent management of suspected cases once they reach the epidemiology services is correct.

In conclusion, it can be said that we will likely witness an increase in measles cases and that we face the challenges of: 1) improving and maintaining vaccination coverage and its monitoring; and 2) improving the capacity to recognize measles cases in the healthcare system.