Don’t ditch mozzie repellent just yet…

By Dr Eddy Bajrovic*

Mosquirix is the world’s first malaria vaccine. Sadly, it’s not the complete solution we’ve been hoping for.
The new vaccine won’t benefit international travellers. Those at risk will have to continue to take anti-malaria medication and use bite-prevention measures to avoid the potentially fatal disease.
Instead, Mosquirix – a combination malaria-Hepatitis B vaccine – will mainly be used to protect young children in the worst-affected areas of Africa.
Developed by GlaxoSmithKline (GSK) and the PATH Malaria Vaccine Initiative, the 3-dose vaccine was found to be effective against falciparum malaria in just 31% of the children aged 6 to 12 weeks who received it, rising to 56% in older children aged 5 to 17 months.
In addition, Mosquirix’s malaria protection wanes after one year, although a fourth dose given as a booster extends its longevity.

Protection for world’s most vulnerable kids

Malaria experts believe Mosquirix can be used alongside existing prevention measures to curb at least some of the world’s estimated 584,000 annual deaths from malaria – especially in sub-Saharan Africa, where children under 4 years are the main victims.
It is anticipated that it will be used to best advantage in protecting children in regions where rates of malaria transmission and mortality are particularly high.
Africa’s malaria burden is the highest in the world. Unlike other infant diseases, the risk of malaria – particularly the often-fatal P.falciparum strain – continues through early childhood, even after repeated infections.
In giving the vaccine regulatory approval outside Europe last week, the European Medicines Agency noted: “Because studies showed that Mosquirix does not offer complete protection, and the protection it provides decreases in the longer term, it is important that established protective measures, for example insecticide-treated bed nets, continue to be used in addition to the vaccine.”
The WHO is expected to make its policy recommendations on how to best incorporate Mosquirix into its vaccination programs by November this year. The agency is anxious that any financing for the drug not draw resources from bed nets, anti-malarial drugs, or rapid diagnostic testing.

Search for new malaria drugs goes on

It has been difficult to assess the true impact of Mosquirix: it was trialled in Africa when bed nets and other interventions were also in use.
And, besides the doubts surrounding its efficacy, other questions remain. 
Will the vaccine deliver a false sense of security in the fight against malaria? Can children living in poor, remote communities be sure of getting all 3 doses on time, as well as the potentially life-saving booster?
Perhaps most pertinent of all, should Mosquirix get the thumbs down while we wait for a better malaria vaccine?
Several other malaria vaccines are in development: one that’s in phase 2 trials is showing some early promise. However, just how effective future malaria vaccines will be and whether they will be suitable for travellers remains to be seen.

Dengue vaccine offers modest protection

With the exception of yellow fever and Japanese encephalitis, developing effective vaccines against mosquito-borne diseases has proven frustratingly difficult and enormously expensive. Decade after decade, one candidate after another has failed, either in development or during trials.
Large-scale clinical trials in Latin America of a much-anticipated but yet-to-be-approved dengue vaccine developed by French pharmaceutical giant, Sanofi Pasteur showed a modest 60% overall rate of protection against the disease, mostly in older children who had previous contact with dengue or similar types of mosquito-borne viruses.
Nor was protection uniform across all four serotypes, ranging from 77.7% for Dengue type 4 to 42.3% for Dengue type 2.
On the plus side, vaccination did substantially decrease the rate of severe dengue cases (95.5%) and hospitalisations (83%).

Aedes mosquitoes conquering the globe

Yet, any protection is better than none and the dengue vaccine will be welcomed by communities at risk as the Aedes mosquitoes continue to expand their geographic range across the globe, aided in no small measure by ever-growing travel and trade.
Before 1970, only 9 countries had experienced severe dengue epidemics; today the WHO estimates there are 390 million cases a year in 128 countries, with no less than half the world’s population at risk of infection. 
Meanwhile, the Chikungunya and Zika viruses – both transmitted by the Aedes species that carry dengue and yellow fever – are also expanding their range dramatically. And, experts agree climate change will increase the spread of both the mosquitoes and the viruses they transmit so effectively.
(A Chikungunya vaccine has shown great promise in early trials, but vaccine development is always painstakingly slow and it could be a decade before it’s available.) 

Disease risk rising for Aussies – home and away

Many Australians are blissfully ignorant of the risk of mosquitoes and the diseases they can carry. For most of us, mozzies are an occasional nuisance at barbeques. 
But, an ever-growing number of travellers are bringing home a nasty memento of their tropical travels.
Already this year 1141 people have returned (mainly from Asia) with dengue fever, 119 have been treated for post-travel malaria, and 79 have been diagnosed with Chikungunya. 
While North Queensland’s annual summer outbreaks of dengue were relatively light with just 60 cases, Australia is having one of its worst-ever years on record for Ross River virus. There have been 7879 confirmed cases of the debilitating virus to date in 2015 – all contracted without leaving the country.

Keep your guard up and avoid bites

It takes just one bite from an infected mosquito for you to get sick. And, it’s especially easy to let your guard down when you’re on holidays.
Until effective vaccines are available, we have to rely on avoiding mozzie bites by:
- Using an effective insect repellent containing DEET, Picaridin, or oil of eucalyptus.
- Getting rid of water-holding containers around your accommodation where mozzies can breed, and
- Either going inside around dusk or changing into long sleeves, long pants, and shoes and socks.
- Sleeping under a permethrin-treated bed net if your room is not screened or air-conditioned. 

Don’t become another travel statistic.
Before you fly, call Travelvax Australia’s travel health advisory service on 1300 360 164 (toll-free from landlines) to learn more about the mosquito-borne diseases at your destination. You can also arrange a consultation to get recommended vaccinations and personalised illness prevention advice from medical professionals experienced in travel medicine.

* Dr Bajrovic is the Medical Director of Travelvax Australia.