By Alison Campbell 04/06/2019


Measles infection has a couple of longer-term sequelae. One, SSPE, is thankfully rare (although for infants with measles the odds of subsequently developing SSPE are considerably higher than for other age groups). The other, “immune amnesia”, is strongly associated with having had measles, though this doesn’t stop those opposed to vaccination claiming otherwise.

In 2015, Mina et al. published a paper in Science that examined the population-level impact of measles infection on overall child mortality from infectious diseases. Infectious disease specialists already knew that

[i]mmunosuppression after measles … predispose[s] people to opportunistic infections for a period of several weeks to months,

which means that, on a population level, vaccination against measles results in a drop in rates of illness and death due to a range of other  infectious diseases.

This suggests that a measles infection somehow suppresses an individual’s immune system for at least several weeks post-infection. Mina & his colleagues knew that other researchers had hypothesised that measles knocks out the patient’s immune memory cells – the long-lasting cells that retain a ‘memory’ of an infection and kick-start an immune response if that pathogen is encountered again. His team wanted to look at this effect in more detail.

They proposed that, if loss of acquired immunity to other diseases after a measles infection really is a thing, then this should show up in epidemiological data and should be apparent in first-world communities where mortality during a measles outbreak is low. To do this they used national data from the US, Denmark, England and Wales that covered the period from prior to the introduction of measles vaccination in those countries to a decade or more afterwards.

After analysing the data, Mina et al. concluded that

[t]hese results provide population evidence for a generalized prolonged (roughly 2- to 3-year) impact of measles infection on subsequent mortality from other infectious diseases.

And furthermore (my emphasis),

when measles was common, MV [measles virus] infections could have been implicated in as many as half of all childhood deaths from infectious disease, thus accounting for nearly all of the interannual fluctuations in childhood infectious disease deaths. The reduction of MV infections was the main factor in reducing overall childhood infectious disease mortality after the introduction of vaccination.

This is only one of several recent studies to find such a link between measles infection & subsequent illness with other infectious diseasees. For example, in 2018 Gadroen et al. published a case-control study of children with and without measles (drawn from a UK database), concluding that

[f]ollowing measles, children had increased rates of diagnosed infections, requiring increased prescribing of antimicrobial therapies. This population-based matched cohort study supports the hypothesis that measles has a prolonged impact on host resistance to non-measles infectious diseases.

A study in macaques (de Vries, McQuaid, van Amerongen et al., 2012) found that measles virus preferentially infected two types of the animals’ immune cells (those involved in immune ‘memory’), which were then rapdily destroyed by other immune cells, with resultant ‘amnesia’. de Vries & his colleagues concluded that

measles virus infection wipes out immunological memory, leaving individuals susceptible to opportunistic infectious agents that would normally be controlled by the immune system.

And subsequently, in a study of unvaccinated children who developed measles during an outbreak in the Netherlands, Laksono et al. (2018) found evidence indicating that measles infection resulted in a decline in memory cells.

Thus, it’s clear that measles suppresses the immune systems of those who’ve had the disease, for around 2-3 years post-infection, most likely by attacking the immune cells that carry a ‘memory’ of previous infectious illnesses. Opponents of vaccination often push the idea that having a wild measles infection “makes your immune system stronger”. They are very, very wrong.

 

R.D. de Vries, S. McQuaid, G. van Amerongen, S. Yuksel, R.J. Verburgh, A.D.M.E. Osterhaus, W.P. Duprex, & R.L. de Swart (2012) Measles immune suppression: lessons from the macaque model. PLoS Pathogens doi:10.1371/journal.ppat.1002885

K. Gadroen, C.N. Dodd, G.M.C. Masclee, M.A.J. de Ridder, D. Weibel, M.J. Mina, B.T. Grenfell, M.C.J.M. Sturkenboom, D.A.M.C. van de Vijver, & R.L de Swart (2018) Impact and longevity of measles-associated immune suppression: a matched cohort study using data from the THIN general practice database in the UK. BMJ Open, 

B.M. Laksono, R.D. de Vries, R.J. Verburgh, E.G. Visser, A. de Jong, P.L.A. Fraaij, W.L.M. Ruijs, D.F. Nieuwenhuijse, H-J. van den Ham, M.P.G. Koopmans, M.C. van Zelm, A.D.M.E. Osterhaus, & R.L. de Swart (2018) Studies into the mechanism of measles-associated immune suppression during a measles outbreak in the Netherlands. Nature Communications 9, Article number: 4944 (2018) doi.:10.1038/s41467-018-07515-0

M.J. Mina, C.J.E. Metcalf, R.L de Swart, A.D.M.E Osterhaus, & B.T. Grenfell (2015) Long-term measles-induced immunomodulation increases overall childhood infectious disease mortality. Science348 (6235), 694-699. doi: 10.1126/science.aaa3662

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