Tuesday, June 6, 2023

After Covid, the travel vaccination deluge

Following the pandemic the return to international travel has put pressure on companies sourcing vaccines, but it’s still vitally important for travellers to protect themselves and not live in a Fool’s Paradise writes Michael McHale

The lifting of pandemic restrictions has brought rates of international travel back to pre-Covid levels, an expert in tropical medicine has found.

Dr Graham Fry, founder and lead medical consultant of the Tropical Medical Bureau, has seen a resurgent appetite from the public for travel, with even the typically quieter off-season months of the year proving to be busier than expected.

“People have just decided that this is the time to travel,” Dr Fry told IMT.

“But after a period of lockdowns, priorities in the wider medical community have changed. With the pandemic years seeing a fall-off in the need for travel vaccinations and other medications, pharmaceutical companies moved their manufacturing to other more in-demand products – chief among them, Covid-19 vaccines.”

As a result, travel medicine is experiencing a major shortage in a number of vaccinations.

“The combined Hepatitis A and B vaccine – that’s apparently in very short supply at the moment. In fact, we can’t get supplies.

“When the drug company provide it, they provide a certain amount for the private market, and the remainder for the HSE. The HSE don’t necessarily take it all up, but they still have the supply allocated to them. That’s left a shortage from the private market point of view, which is causing difficulties.”

While the Tropical Medical Bureau does have supplies of the vaccine for Hepatitis A, the lack of availability of the combined A and B vaccine is leaving unprotected travellers susceptible to Hepatitis B, an infection that can be passed on through sexual activity or blood transfusions.

To address the issue in the short-term, questions inevitably arise about whether the HSE’s supplies could be better redistributed.

“The real danger with the HSE is – like with their flu vaccine and many other vaccines – they buy in bulk. And like their Covid vaccine – the question is how many doses were actually wasted? There’s always that difficulty.

“You can argue that you’re better to have supplies and not use them, than not to have supplies. You can understand that. But at the same time, there should be some give-and-take.

“If people do come home with Hepatitis, the end result of that will be definitively against the HSE. It’ll fall to them to look after those people.”

Dr Fry’s clinics are also experiencing shortages in the cholera vaccine, due to global supplies being prioritised to deal with outbreaks in Haiti and Malawi. “I’m not terribly worried about that one. It’s not such a big issue – it’s just more of a nuisance than anything else.

“But there’s always a question of what supplies you have available, and companies trying to catch up after the quietness of the last three years.”

“Certainly one of the vaccine companies has moved its production towards Covid vaccines and away from some of the standard travel vaccines. For instance, the combined Hep A/Typhoid vaccine, which we used for years – we haven’t been able to get at all. That’s gone for about six months now. The reason, they tell us, is that they were concentrating on the Covid vaccine. Whether that will come round or not, it’s very hard to tell.”

While some current vaccines are proving difficult to source, newer vaccines are giving hope in the battle against other diseases more commonly found abroad.

The European Medicines Agency recently approved a new vaccine to protect against the dengue virus, a mosquito-borne tropical disease that leads to 390 million infections globally each year, and up to 25,000 deaths.

The new vaccine offers some protection against dengue types one, two, three and four.
While there is another previously approved vaccine for dengue, the new inoculation has shown a wider protection for young children and people over 45.

“That older vaccine – you had to give it to people who had already developed dengue,” Dr Fry explained. “If you gave it to somebody who hadn’t developed dengue and then they got it from one of the other types, it would be much more severe. Therefore, tourists wouldn’t be using it.”

The new vaccine can be given to people who never previously had the virus and, after two doses were given, was shown in research studies to reduce the rate of fever caused by dengue by 80 per cent among children within a year.

The vaccine also reduced hospitalisation due to dengue by 90 per cent. The vaccine is based on a live-attenuated dengue type 2 virus. As a live vaccine,

Dr Fry is cautiousabout how it may interfere with other inoculations prospective tourists may receive.

“Being a live vaccine, it may interfere with the yellow fever vaccine, so you need to keep them separate. Another thing to bear in mind is it’s a subcutaneous injection rather than intramuscular – it’s a different technique in giving the vaccine. And the other final thing is that it needs to be given on two occasions, three months apart. How many people are going to turn up three months ahead of time for a vaccine against a disease that is relatively uncommon for tourists? Of course, there are tourists that get it, but nevertheless, the vast majority don’t.”

Significant advancements have already been made in the race for an effective malaria vaccine, with one such shot, developed by the University of Oxford, receiving approval in Ghana in April. Ghana is the first country in the world to authorise the inoculation, which can now be given to children aged 5-36 months there.

However, Dr Fry believes it in unlikely that the vaccine will be of much use to travellers from countries outside of those directly impacted by malaria.

“In west Africa there are people dying from this disease, so anything we can do to help them is better. However, in this part of the world where you don’t have those diseases, giving a vaccine which provides somewhere in the region of 30, 40 or 50 per cent cover in some cases – that’s not sufficient,” he added.

“For the traveller, you always need to have a vaccine that’s going to provide over 90 per cent protection. If it’s less than 90 per cent you end up with a fool’s paradise – somebody who thinks they’re protected when they aren’t. So from a malaria point of view, the chances of having a tourist vaccine available in the near future is not that great. It’ll be a while off yet.”

Closer to home, other conditions which have so far have evaded vaccines include leishmaniasis, a parasitic disease found in southern Europe.

“That can present as what appears to be a mosquito bite that doesn’t heal – that’s a parasite that’s gone in under your skin. There is a version of that that can get into your spleen or liver and can actually kill people – that’s called kala-azar. That’s in the Mediterranean – how many people do we have going down there?”

Dr Fry also pointed to a recent assessment that showed a likelihood that tick-borne encephalitis virus is present in southern England. While overall risk in the UK remains low, the virus can cause a range of illnesses, from mild flu-like symptoms, to severe infection in the central nervous system such as meningitis or encephalitis.

“Ireland is so fortunate. We have a climate which means we don’t have the problems that many other countries do,” Dr Fry added. “But the difficulty is people travel, and when they travel they turn off their common sense, which is the biggest problem.”

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