The ovation was loud. It was
also global. It rages still. At last, an end seem in sight to the killer
disease: malaria. A vaccine has been discovered. It is called Pf-SPZ.
But will this vaccine finally bring an end to the scourge of the tropics
and Africa? Or will it go the way of its predecessor and never see the
light of the market?
The news was received with a lot of jubilation not only in Africa but
around the globe. An investigational malaria vaccine developed by
scientists at Sanaria Inc. and known as PfSPZ Vaccine has been found to
be safe, to generate an immune system response, and to offer protection
against malaria infection in healthy adults. This, the pharmaceutical
firm ascribed to the results of an early-stage clinical trial. Why the
huge celebration and global excitement? Malaria poses a tremendous
public health problem. The World Health Organisation (WHO) estimated that in 2010, there
were 219 million cases of malaria (with an uncertainty range of 154
million to 289 million) leading to approximately 660,000 deaths (with an
uncertainty range of 610 000 to 971 000), mostly among African
children. Between 2000 and 2010 malaria mortality rates fell by more
than 25 per cent globally. Most deaths occur among children living in
Africa where a child dies every minute from malaria. According to WHO country-level burden estimates available for 2010 an
estimated 80 per cent of malaria deaths occur in just 14 countries and
about 80 per cent of cases occur in 17 countries. Together, the Democratic Republic of the Congo and Nigeria account
for over 40 per cent of the estimated total of malaria deaths globally.
The highest levels of Plasmodium falciparum, the deadliest malaria
parasite, are found in Africa. It has been estimated that 342 million
people remained exposed to this very high transmission risk in 2010. The
PfSPZ Vaccine is composed of live but weakened sporozoites of the
species Plasmodium falciparum, the most deadly of the malaria-causing
parasites. Sanaria Inc, the United States based drug firm is, however, not the
first to embark on finding a vaccine for the ravaging disease. An
attempt had been made earlier by GlaxoSmith- Kline. Some years ago when
the British drug firm announced its breakthrough on malaria vaccine, it
was also well celebrated. Subsequent monitoring and results have,
however, proved that the effect of the vaccine waned as time progressed
thereby creating a soft underbelly in the once acclaimed medical
breakthrough. According to Reuters, the effectiveness of an experimental malaria
vaccine developed by GlaxoSmith- Kline waned over time, with the shot
protecting only 16.8 percent of children over four years, according to
trial data. Results from a separate trial last year showed the vaccine was only
30 percent effective in babies. “The results are kind of disappointing
because we’d all like to see a malaria vaccine that has closer to 80
percent or 100 percent efficacy,” the media agency quoted Christopher
Plowe, a malaria researcher at the University of Maryland School of
Medicine in the United States, who was not involved in the RTS,S trial. Published in the New England Journal of Medicine on Wednesday, the
new data found that although RTS,S initially had a protection rate as
high as 53 percent, after an average of eight months that effectiveness
faded swiftly. GSK’s study involved 447 children in Kilifi, Kenya, who
had been part of a mid-stage, or phase II, trial to assess the safety
and efficacy of RTS,S. Of the 447 children, 320 were able to be followed
up for four years.
However, the recently announced PfSPZ Vaccine clinical evaluation
which was conducted by researchers at the National Institute of Allergy
and Infectious Diseases (NIAID) in the US in its Phase I enrolled 57
healthy adult volunteers between the ages 18 to 45 years who never had
malaria. Of these, 40 participants received the vaccine and 17 did not. To evaluate the vaccine’s safety, vaccinees were split into groups
receiving two to six intravenous doses of PfSPZ Vaccine at increasing
dosages. After vaccination, participants were monitored closely for
seven days. No severe adverse effects associated with the vaccine occurred, and
no malaria infections related to vaccination were observed. Based on
blood measurements, researchers found that participants who received a
higher total dosage of PfSPZ Vaccine generated more antibodies against
malaria and more T cells—a type of immune system cell—specific to the
vaccine. To evaluate whether and how well the PfSPZ Vaccine prevented malaria
infection, each participant— the vaccinees as well as the control group
that did not receive vaccine—was exposed to bites by five mosquitoes
carrying the P. falciparum strain from which the PfSPZ Vaccine was
derived. This controlled human malaria infection procedure—a standard
process in malaria vaccine trials—took place three weeks after
participants received their final vaccination. Participants were monitored as outpatients for seven days and then
admitted to the NIH Clinical Center, where they stayed until they were
diagnosed with malaria, treated with anti-malarial drugs and cured of
infection, or shown to be free of infection. The researchers found that the higher dosages of PfSPZ Vaccine were
associated with protection against malaria infection. Only three of the
15 participants who received higher dosages of the vaccine became
infected, compared to 16 of 17 participants in the lower dosage group
who became infected. Among the 12 participants who received no vaccine,
11 participants became infected after mosquito challenge
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