I thought flu season was over

By Dr. Goldman from ParkwayHealth 2019-05-23 15:59:54

How to protect yourself when flu season lingers on

The flu season may not be done with – nevertheless, the peak seems to be behind us, at least in China. In Europe, they seem to only feel the ‘heat’ of infections now. Most people I saw with the flu had Influenza A (H3N2 or H1N1), and not Influenza B. Interestingly, amongst all the sick kids and adults, several of them had been vaccinated against the flu. So, no, the influenza vaccine doesn’t appear to be too effective - more on that later.

The other issue is about treatment: there is an antiviral drug that can be used against influenza. But then when should we receive it and how well does it work?

Preventing the Flu

Can we avoid the flu? For most of us, the chance that we escape the virus altogether is very slim – unless one has good immunity against the currently circulating flu strain, typically from a previous infection or vaccination. So why is this popular vaccination still relatively ineffective?

Because the flu virus mutates constantly, the vaccine must be adapted annually to remain effective. The WHO’s experts decide every year which flu virus strain they think will cause most infections and those strains are then used by manufacturers to produce vaccines in hens’ egg embryos. It is hoped that the chosen strains will correspond with the virus circulating during the following winter. If the strain is not a good match… well, vaccinated people may still get the flu.

Another issue may be that the flu virus grown in embryos becomes slightly different to the original strain, perhaps owing to the culture conditions, and loses the ability to generate the right antibodies against the flu virus we are exposed to.

So is the vaccine over-hyped? No. Ideally the vaccine should prevent us from becoming sick in the first place. But even if we do get sick, being vaccinated actually decreases the chance that we become seriously sick: it can make the difference between being miserable in bed at home for two days and being incubated in an intensive care unit for three weeks. Now, granted, we take the vaccine for ourselves because we don’t want to miss work or holidays. We don’t take it because we think we can avoid a serious illness. Indeed, for most of us the disease is mild or severe, but not serious.

This leads us to the other, more important aspect of vaccination: limiting the spread of the illness to help protect those most at risk, usually the old, the very young and those with a chronic illness. Among these, most can be vaccinated but some may not respond effectively to the vaccination, including (ironically) those most at risk of a serious influenza infection. Having vaccinated people around them will decrease the chance that the virus reaches them. That is what we call the herd effect. Such vaccination includes that of pregnant women, to protect their newborn babies later (who will be still too young to be vaccinated).

Treating the Flu

Now let’s say you’ve caught the flu: what can you do about it? Take an antiviral like Oseltamivir (Tamiflu ®, Roche). Oseltamivir is like an antibiotic but against influenza. But why would we take it since, as we saw, the flu is usually not a serious illness for most people?

Oseltamivir has been found to decrease flu symptoms by a mean 29 hours in kids and 16.8 hours in adults (Cochrane systematic review). Another systematic review, supported by Roche (unsurprisingly) found more favorable effects.

Of course there is a price to pay for a reduction in the duration of symptoms with Oseltamivir, including vomiting in 5.3% of kids and significant decrease in the production of antibodies against influenza among the populace to name only a few of them. Every time we use the drug, we increase the chance of viral resistance against it.

The rationale for offering Oseltamivir, from a public health point of view, is to avoid those potentially serious cases of influenza. It is likely to be more effective when given early in the course of the illness. The irony is, however, that it is still unclear whether Oseltamivir can actually prevent more serious influenza or change the outcome of an already serious case. But since nothing else is available and the disease is potentially serious, we use it.

By offering Oseltamivir to pretty much everybody with suspected influenza, countries like the US push the doctors to use the drug on a much broader population, thereby increasing the chance of resistance and also the number of cases of adverse effects. On the other hand, the more restrictive European use of the drug among those kids and adults with a serious chronic illness or those with serious influenza is bound to minimize the push towards drug resistance and confine drug side effects to a smaller population of patients.

No matter where we stand in this discussion, it is difficult to justify the use of Oseltamivir for healthy adults and children older than two to five years of age with an uncomplicated influenza: in such a population, with whom we would be very unlikely to prevent anything potentially serious, we would have lots of drug-related vomiting, and would massively increase the risk of resistance. All this to gain a few hours of comfort that paracetamol could bring at least as effectively.

In conclusion, getting vaccinated against the flu may not be a panacea, but it’s still the best way to prevent the flu. Antivirals may be warranted in some cases, but one should be careful to think before using them due to the risk of minimizing viral resistance, especially because the prevention potential of Oseltamivir et al is not well established. After all, this drug is currently the only one available in case of a serious influenza pandemic, when its effectiveness really might be a matter of life and death.

Dr. Nathanael Goldman


Dr. Nathanael Goldman is a pediatrician with over 20 years of international experience in pediatrics. He received his Postgraduate degree in Pediatrics at the Universite Libre de Bruxelles (Belgium), and has been working as a pediatrician in international clinics in Belgium, Beijing, and now at ParkwayHealth in Shanghai.


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