The Turnstone: talking about vaccines #37
The Turnstone: talking about vaccines #37
Malaria and dengue (4 minute read)
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Back in January, I looked at mosquitoes, climate change and the fight against malaria. At the time, I mentioned that there was a malaria vaccine which had recently become available, but it wasn’t particularly effective – reducing severe disease by 30%. In the absence of anything better, it was being used to vaccinate those most at risk – young children in sub-Saharan Africa. But we needed to do better.
Then, a couple days ago, I heard something on the news. The Jenner Institute at Oxford University, the people who developed the Oxford-AstraZeneca vaccine for Covid-19, have developed a new vaccine for malaria. Ghana has evaluated the safety and efficacy of the vaccine and has approved it for use. The vaccine still needs to be evaluated by the World Health Organisation before it becomes more widely used. However, it is reported to have an efficacy of over 75% against clinical malaria. This is a big improvement on the previous vaccine.
So, does this mean that a malaria vaccine will be added to the list of potential vaccines for travellers? Will we be able to take a dose and forget about the malaria risk?
At this stage, no. The vaccine has been developed for and tested on those most at risk of dying from malaria, young children. Nor is the efficacy likely to be high enough to negate the threat of this extremely common disease. In 2021, there were nearly 250 million malaria cases. If you are in an area with malaria and you don’t take precautions to prevent mosquito bites, you’ve got a good chance of catching it.
The picture is similar for dengue fever, which is the other prevalent mosquito-borne disease. There is a vaccine, but it’s not a vaccine for general use. I’ve put more information about the dengue vaccine in the section about dengue below.
At the time I was writing about mosquitoes and malaria, I intended to share some of the resources I found, but I ended up writing about other topics. So, I thought I would share them now. This information is largely aimed at people who don’t live in areas with malaria and dengue, but may travel to places where the diseases, and mosquitoes which carry them, occur.
Prevent mosquito bites
The first and most important defence against malaria and dengue is to avoid getting bitten by mosquitoes in areas where these diseases are present.
The UK’s National Health Service has the best guide I’ve found on avoiding mosquito bites, including details on insect repellent, clothing and bed nets.
Mosquito Bite Avoidance - Fit for Travel (6 minute read)
There is also some more detailed information on insect repellents from New Zealand’s health navigator website.
Insect repellents | Health Navigator NZ (6 minute read)
If you prefer a video, there’s some basic information on this web page about dengue fever from New Zealand’s Ministry of Health. However, the two pages I’ve listed above give more specific detail.
Dengue Fever | KidsHealth NZ (2 minute video)
Malaria
The USA Centres for Disease Control has some useful pages about malaria. The first link here is general information aimed at people from the USA travelling to areas with malaria, but it is relevant for others who come from areas without malaria. It also links to specific information by country, since different countries have different mosquitoes and different types of malaria.
CDC - Malaria - Travelers (4 minute read)
Although there isn’t a malaria vaccine suitable for travellers, there are drugs which can be taken to prevent or treat the disease. All have advantages and disadvantages, and decisions on which drugs to take need to be made with the help of a health professional. However, the following page gives some useful background information.
CDC - Malaria - Travelers - Choosing a Drug to Prevent Malaria
The following fact sheet from the Auckland Regional Public Health Service also gives an overview of malaria.
Malaria fact sheet (arphs.health.nz) (4 minute read)
For more detailed information, the World Health Organisation website is a good place to look.
Malaria (who.int) (8 minute read)
Dengue fever
New Zealand’s health navigator website has a good guide to dengue fever, especially aimed at those travelling to areas with dengue. The main point is that there aren’t specific preventatives or treatments for dengue, so it’s best to avoid mosquito bites. Another important point about dengue is that you aren’t immune after you’ve had it. In fact, severe dengue is more likely in those who have had dengue before.
Dengue fever | Health Navigator NZ (8 minute read, 2 minute video)
The USA Centres for Disease Control has a page which gives the dengue risk for different countries.
Dengue Around the World | Dengue | CDC
The World Health Organisation has more information about dengue fever.
Dengue and severe dengue (who.int) (7 minute read)
There has been one vaccine approved for dengue fever in some countries, but it is only for those at higher risk of a severe case, that is, those who have previously had dengue. The vaccine is approved for children aged 9-16 in the USA. It is not available in New Zealand.
Dengue Vaccination: What Everyone Should Know | CDC (6 minute read)
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