Featured Research

from universities, journals, and other organizations

Follow-up study describes declining efficacy of malaria vaccine candidate over 4 years

Date:
March 20, 2013
Source:
Wellcome Trust
Summary:
Long-term follow-up of a phase II study from researchers in Kenya shows that the efficacy of a malaria vaccine candidate, RTS,S, wanes over time and varies with exposure to the malaria parasite.

Long-term follow-up of a phase II study from KEMRI-Wellcome Trust Research Programme and Oxford University researchers in Kenya shows that the efficacy of a malaria vaccine candidate, RTS,S, wanes over time and varies with exposure to the malaria parasite.

The findings will help to inform which populations are likely to benefit most from the vaccine candidate. They also have important implications for the design of future clinical trials of this and other vaccine candidates and highlight the importance of long-term follow-up studies for assessing vaccine efficacy.

The study involved 447 children in Kilifi, Kenya, who had been part of an earlier phase II trial to assess the safety and efficacy of the vaccine candidate. Of the 447 children, 320 completed four years of follow-up. The analysis, which was published today in the New England Journal of Medicine, was designed to look at how well the vaccine candidate protects against malaria over time.

Initial results from larger ongoing phase III studies showed that the candidate RTS,S vaccine reduced malaria over 12 months of follow-up by approximately half in young children and one-third in infants. The new findings on long-term follow-up of an earlier phase II study reveal that the vaccine efficacy dropped from 43.6 per cent protection against malaria in the first year to zero by the fourth year after vaccination.

The study's senior author, Dr Phillip Bejon (Research Fellow at the KEMRI-Wellcome Trust Research Programme and the Centre for Tropical Medicine, University of Oxford), said: "Despite the falling efficacy over time, there is still a clear benefit to the vaccine candidate. Many of the children will experience multiple episodes of clinical malaria infection, but overall we found that 65 cases of malaria were averted over the four-year period for every 100 children vaccinated. We now need to look at whether offering a vaccine booster can sustain efficacy for longer."

The study also shows that relative vaccine efficacy declines with increasing exposure to malaria, from 45.1 per cent among children with below-average exposure to malaria to 15.9 per cent among children with above-average exposure to malaria. The relative efficacy describes the number of cases of malaria that were avoided by vaccination as a percentage of the total number of cases in that group: because there were many more cases of malaria at higher exposure, the cases averted per 100 children vaccinated actually increased from 62 at below-average exposure to 78 at above-average exposure.

The study's lead author, Dr Ally Olotu, a Wellcome Trust PhD student at the KEMRI-Wellcome Trust Research Programme and Oxford University, explains: "We need to consider whether relative efficacy or absolute number of cases averted is the more informative measure. In any case, these are important findings that will help to inform which populations are likely to benefit most from the vaccine.

"The ongoing phase III study will provide further insights to the vaccine's efficacy in different settings of malaria exposure and includes an assessment of a booster dose to sustain efficacy over time."

Malaria remains an important cause of illness and death among children in sub-Saharan Africa, and there is currently no vaccine that offers complete protection against the disease. RTS,S is the most advanced candidate malaria vaccine and entered phase III clinical trials in Africa in 2009. The vaccine candidate seems to be well tolerated and has an acceptable safety profile, but it remains unclear which sub-groups of children might benefit most and what the duration of efficacy is.

Jimmy Whitworth, Head of International Activities at the Wellcome Trust, said: "This study indicates the durability of protection of a single initial course of this vaccine against malaria, and the variability of protection at different levels of exposure to malaria. These are key pieces of information required for us to understand how best to use this vaccine and the regimes of boosters that will be required to provide optimum protection."

Latest figures estimate that there are 1.44 billion people living in regions of stable malaria transmission worldwide. Most deaths occur among children living in Africa, where a child dies from malaria every minute.


Story Source:

The above story is based on materials provided by Wellcome Trust. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ally Olotu, Gregory Fegan, Juliana Wambua, George Nyangweso, Ken O. Awuondo, Amanda Leach, Marc Lievens, Didier Leboulleux, Patricia Njuguna, Norbert Peshu, Kevin Marsh, Philip Bejon. Four-Year Efficacy of RTS,S/AS01E and Its Interaction with Malaria Exposure. New England Journal of Medicine, 2013; 368 (12): 1111 DOI: 10.1056/NEJMoa1207564

Cite This Page:

Wellcome Trust. "Follow-up study describes declining efficacy of malaria vaccine candidate over 4 years." ScienceDaily. ScienceDaily, 20 March 2013. <www.sciencedaily.com/releases/2013/03/130320212814.htm>.
Wellcome Trust. (2013, March 20). Follow-up study describes declining efficacy of malaria vaccine candidate over 4 years. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2013/03/130320212814.htm
Wellcome Trust. "Follow-up study describes declining efficacy of malaria vaccine candidate over 4 years." ScienceDaily. www.sciencedaily.com/releases/2013/03/130320212814.htm (accessed July 22, 2014).

Share This




More Health & Medicine News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Courts Conflicted Over Healthcare Law

Courts Conflicted Over Healthcare Law

AP (July 22, 2014) Two federal appeals courts issued conflicting rulings Tuesday on the legality of the federally-run healthcare exchange that operates in 36 states. (July 22) Video provided by AP
Powered by NewsLook.com
Why Do People Believe We Only Use 10 Percent Of Our Brains?

Why Do People Believe We Only Use 10 Percent Of Our Brains?

Newsy (July 22, 2014) The new sci-fi thriller "Lucy" is making people question whether we really use all our brainpower. But, as scientists have insisted for years, we do. Video provided by Newsy
Powered by NewsLook.com
Scientists Find New Way To Make Human Platelets

Scientists Find New Way To Make Human Platelets

Newsy (July 22, 2014) Boston scientists have discovered a new way to create fully functioning human platelets using a bioreactor and human stem cells. Video provided by Newsy
Powered by NewsLook.com
Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

TheStreet (July 21, 2014) New research shows Gilead Science's drug Sovaldi helps in curing hepatitis C in those who suffer from HIV. In a medical study, the combination of Gilead's Hep C drug with anti-viral drug Ribavirin cured 76% of HIV-positive patients suffering from the most common hepatitis C strain. Hepatitis C and related complications have been a top cause of death in HIV-positive patients. Typical medication used to treat the disease, including interferon proteins, tended to react badly with HIV drugs. However, Sovaldi's %1,000-a-pill price tag could limit the number of patients able to access the treatment. TheStreet's Keris Lahiff reports from New York. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins