With Covid-19 figures generally heading south (touchwood and all that!), the big news of the week focussed on older ailments with the bat virus being replaced by the unfriendly neighbourhood mosquito.
More than 130 years after the naming of the Plasmodium parasites behind malaria, the world now has its first approved vaccine against them. Many malaria researchers have celebrated the development, but others have expressed concerns over the deployment of a vaccine that has only moderate efficacy. (www.nature.com/articles/d41586-021-02755-5)
In a news release on 6 October, the World Health Organization (WHO) backed the vaccine — called RTS,S — and recommended its widespread use among children in sub-Saharan Africa, which is home to the deadliest malaria parasite, Plasmodium falciparum. (www.who.int/news/item/06-10-2021-who-recommends-groundbreaking-malaria-vaccine-for-children-at-risk)
“The RTS,S malaria vaccine — more than 30 years in the making — changes the course of public health history,” said WHO director-general Tedros Adhanom Ghebreyesus at a press briefing announcing the endorsement.
Compared with other childhood vaccinations, RTS,S has only modest efficacy, preventing about 30% of severe malaria cases after a series of four injections in children under the age of five.
Nevertheless, one modelling study suggests that it could prevent the deaths of 23,000 children a year, if the full series of doses were given to all kids in countries with a high incidence of malaria — making a significant dent in the tremendous toll of the disease, which killed 411,000 people in 2018.
The development and testing of the vaccine also known by its brand name, Mosquirix, has been on since 1987, at a cost of more than US$750 million. This was funded mainly by the Bill & Melinda Gates Foundation in Seattle, Washington, and the London-based pharmaceutical firm GlaxoSmithKline (GSK).
Although clinical trials concluded in 2015, the WHO then recommended pilot studies to determine the feasibility and safety of this multi-dose vaccine outside a clinical trial.
Gavi, the Vaccine Alliance, helped fund the pilot programmes, which have distributed 2.3 million vaccine doses across Ghana, Kenya and Malawi reaching 800,000 children since 2019. Gavi reports that in these studies, hospitalisations from severe malaria decreased by about 30%. The pilot results prompted the WHO to recommend that four doses of the vaccine be given to children living in regions with moderate to high levels of malaria transmission.
In addition to deciding how to deploy the vaccine, countries will need to determine how much it will cost to purchase and distribute it — and whether donors will help foot the bill.
The vaccine manufacturer GSK released a statement pledging to make 15 million doses available annually at just above the cost of production. However, roughly 100 million doses will be needed annually if all children in high burden countries are to receive the shots.
At a potential cost of about $5 per dose, researchers suggest the vaccine rollout, including its distribution, would cost around $325 million to administer each year across 10 African countries with a high incidence of malaria. But then, more than 260,000 African children under the age of five die from malaria annually which should put a different perspective on the issue.
Relief may be in sight for tropical hospitals that are increasingly overwhelmed during outbreaks of dengue, another mosquito-borne viral disease that can cause excruciating pain and even death. A new study has identified a compound that blocks dengue virus replication in test tube experiments and in mice, and it might one day be available as an easy-to-take pill. (www.science.org/content/article/first-drug-dengue-excruciating-disease-may-be-horizon?1)
If it works in clinical trials in humans, the drug could be given at primary care clinics, very important for the developing world where dengue is hyper-endemic.
Dengue, which is spread by mosquitoes that thrive in urban areas, annually infects more than 400 million people, primarily in Asia and Latin America. Most cases are mild, and patients recover on their own. But an estimated 96 million people come down with bad fevers, rashes, and muscle and joint aches that can last about a week. It is commonly called “breakbone fever” because of the severity of its symptoms. The disease is caused by four related viruses, or serotypes; subsequent infection with a different serotype increases the risk of internal bleeding and death. There are no drugs for it at present. During outbreaks, scores of patients with severe dengue rely on hospital care to manage the life-threatening symptoms.
The need to simultaneously protect against all four serotypes has stymied dengue vaccine development for decades. Finding a drug with balanced activity against all four was “like finding a needle in a haystack,” says Johan Neyts, a virologist at KU Leuven who led the study.
The drug is already in clinical trials, but Neyts declines to give details, saying scientists will present an update in November at the annual meeting of the American Society of Tropical Medicine & Hygiene. He also doesn’t want to hazard a guess as to when a drug might become available.
And can we rest without at least a routine genuflection in the direction of the ruling global deity, Covid-19 or better still its gradual retreat? Pfizer and BioNTech said Thursday they are seeking US Food and Drug Administration emergency use authorization (EUA) for their Covid-19 vaccine for children ages 5 to 11. (https://edition.cnn.com/2021/10/07/health/hfr-pfizer-covid-vaccine-fda-eua/index.html)
If authorised, this would be the first Covid-19 vaccine for younger children. The Pfizer/BioNTech vaccine is approved for people age 16 and older and has an EUA for people ages 12 to 15.
Last month, Pfizer released details of a Phase 2/3 trial that showed its Covid-19 vaccine was safe and generated a “robust” antibody response in children aged 5 to 11. The trial included 2,268 participants aged 5 to 11 and used a two-dose regimen of the vaccine administered 21 days apart.
Pfizer began submitting its data on the vaccine for younger children to the FDA late last month, but had not formally requested authorization until now.
FDA officials had said that once vaccine data for younger children was submitted, the agency could authorize a vaccine for younger children in a matter of weeks — not months — but it would depend on the timing and quality of the data provided.
Even as parents in the United States wrestle with difficult questions over vaccinating their children against the coronavirus, families in other countries have been offered a novel option: Giving children just one dose of the vaccine. Officials in Hong Kong as well as in Britain, Norway and other countries have recommended a single dose of the Pfizer-BioNTech vaccine for children aged 12 and older — providing partial protection from the virus, but without the potential harms occasionally observed after two doses. Health officials in those countries are particularly worried about increasing data suggesting that myocarditis, an inflammation of the heart, may be more common among adolescents and young adults after vaccination than had been thought.
