Q&A #15 : Should I rush to get my young child vaccinated against monkeypox?

That would normally be the thing to do; however, given the unusual circumstances of exposure (C-19 pandemic), even young children got meanwhile largely exposed to SARS-CoV-2 (not at least by their parents!). I am aware of several cases where young children got already infected at a very early age (4-8M) showing only (very) mild symptoms. So, in the absence of an adequate smallpox vaccine, the best things to do is to simply engage them as of an early age (ideally before 8 Ms) in the 'free' training sessions that are now available everywhere in highly vaccinated countries! This is the time where they have high concentrations of innate Abs that will protect them from typical seasonal and airborne childhood infections while already allowing their innate immune system to train. If they miss out on training during this time, they'll will need to rely on productive infection later on to gain natural immunity which inevitably implies some form of disease (i.e., they do no longer get a 'free' ride). This being said, it is important to bear in mind that training is per definition a continuing exercise and it probably takes several exposures before the innate immune system can withstand a high viral load or a more infectious variant. Children and youngsters who successfully countered a first viral encounter and only developed asymptomatic/ mild infection will develop short-lived, nonfunctional anti-spike antibodies. As those will not neutralize the virus, they have infection-enhancing capacity and, therefore, pose a challenge to the capacity of incompletely trained NK cells. The threat , however, is only short-lived as these antibodies are no longer detectable after 8 weeks. However, if the viral infection rate in the population is high and/ or the circulating virus is highly infectious (Omicron!), then there is a reasonable likelihood that children get re-infected during that short period of time following their first asymptomatic infection. These are typically the cases where even children without predisposing health factors or underlying disease can get severe diseases and require hospitalization. This is undoubtedly a direct consequence of the mass vaccination campaigns that drove the dominant expansion of highly infectious viral variants (Omicron).  

Anyone whose immune system  has been properly trained to ward off coronaviruses and , therefore, also monkeypox virus cannot experience any harm from a smallpox vaccine as the virus will be eliminated on the spot by the trained NK cells. But please, remember that for young children who are otherwise immunologically naïve, it is still good practice to vaccinate them against measles, mumps, rubella, (varicella), Hib and meningitis (MenACWY) during the time where Nature guarantees them a 'free ride'. If they aren't given that opportunity, they will need to catch up on training via contracting the disease upon subsequent exposure to the wild virus/ bacterium. However, if that exposure occurs within a context of high infectious pressure (e.g., outbreak of measles), children will become more likely to contract severe disease (and sometimes even death) for the reasons explained above.

But let's be crystal clear: Once you got your child vaccinated with any of the current C-19 vaccines, it will no longer be possible to kick off training of its innate immune system against seasonal respiratory and classical childhood infections. The vaccinal antibodies will simply outcompete the innate antibodies for binding to the virus as their affinity for the target protein (e.g., spike protein in case of Sars-CoV-2) is much higher. Unless the training got kicked off, the NK cells don't get educated on which viral motifs they should watch out for. When you miss that kick-off, you irreversibly loose the opportunity to sensitize your cell-based innate immune system (NK cells), no matter how many times your child gets exposed to these viruses or vaccinated against them after it got the Covid shot (all C-19 vaccines used are non-replicating vaccines!). Innate polyspecific antibodies enable the kick-off whereas vaccinal, antigen-specific antibodies prevent it. That is why we're not administering any non-replicating viral vaccine to young children! Antigen-specific antibodies are welcome but to control this type of viruses, they need to come after the NK cells got educated on which pathogen-derived patterns to recognize. If they come first, they'll just prevent NK cells from recognizing those patterns.