It is not news that it is normal at this time of the year for cases of viral respiratory infections, such as Respiratory Syncytial Virus (RSV) and Influenza, to increase and cause outbreaks. Neither is unusual that bacterial infections also rise as they tend to appear after or with a viral infection. However, what is new is that we might be more vulnerable this year due to a now so-called “immunity debt”.
Personally, I think this is not a good term and I hadn’t seen the use of it before Covid19 pandemic. Is there any evidence for using it? Does “immunity debt” exist? I would favour the use of a better term. Maybe innate immunity decrease. Even so, exposure to one single vaccine, whichever it is, can train our innate immunity and enhance it. What about herd immunity decrease?
The appearance of the “immunity debt” term
“Immunity debt” started to spread from an opinion paper published in August 2021 where the authors aim was to check the effects of non-pharmaceutical interventions (NPI) imposed by the SARS-CoV-2 pandemic on the appearance of larger epidemics. Their idea was that these interventions reduced the spread of the other pathogens during lockdown periods, as people didn’t interact within the community as much, since they were spending more time at their homes.
Consequently, the lack of immune stimulation and the reduced vaccine uptake induced an “immunity debt”. The authors even mentioned the possibility of a decreased herd immunity due to the observed delay in the vaccination programme that also didn’t include vaccines against rotavirus, varicella and some others. I should stress that this study was carried out in France.
When I think of what the authors suggested about lockdowns imposed in 2020 being responsible for an “immunity debt”, my thoughts go back centuries. Are the authors applying Lamarckian’s theory to our immune system such as — if we don’t use it, it atrophies? Our immune system doesn’t require constant activation from pathogens for it to be functional.
Something to bear in mind also. Children, in lockdowns or not, are in contact with bugs all the time!! Bugs from food, from their parents and from their gardens. I bet from the computer screens as well, during their online school sessions.
What could be the reason for these high levels of RSV and Streptococcus A (Strep A) infections?
One hypothesis is that infants that normally get infected during their first two to five years of life didn’t, and therefore, instead of having staggered infections in these last years, children are getting infected at the same time and for the first time ever in their lives, making the outcome more severe.
Consequently, pressure on hospitals increases substantially. One could argue then that this is an immunity debt. But is it? Or is it just an immunity interruption? We don’t lose immunity, so it can’t be a debt. It can be a delay of immunity for those who have never encountered the pathogen before and that is why vaccination programmes exist.
The danger of this concept of “immunity debt” is that it supports those against Covid19 vaccine with the argument that Covid19 is like a bad flu and that it is good to get infected with it to provide immunity in the longer term. This thought is wise, isn’t it? We, scientists, ask: why would someone want immunity from an infection? The ones preferring to get infected respond: to be protected from getting infected…oh…oh! Suddenly the realisation of their poor thinking comes to surface!
Or likewise, we, scientists, ask: why are so many vaccines so successful that some of them even eradicated diseases such as Smallpox, Polio, Hepatitis B, Meningitis, Measles, Mumps and Rubella in the past? It is because they conferred immunity. The ones that don’t believe in vaccines answer: then, why are some of these diseases re-appearing? We, scientists, respond: because some young children are not being vaccinated anymore!
We need to keep all causative links on the table
For the cases of Strep A bacterial infection, I believe it is an example of an opportunistic infection due to viral infections, such as RSV, influenza or even Covid19 itself as the age group of children affected hasn’t been vaccinated for SARS-CoV-2.
There is no doubt that immunity surveillance is an important public health matter. There is need to understand well the fluctuation on the levels and on the times of the year of these infections. However, it is fundamental to keep all the possible causative links to these high levels of RSV and Strep A infections on the table. We don’t have surveillance in place for SARS-CoV-2 as we have for other infections. Do we?!
