Virus World

A new vaccine for dengue received prequalification from the World Health Organization (WHO) on 10 May 2024. TAK-003 is the second dengue vaccine to be prequalified by WHO. Developed by Takeda, it is a live-attenuated vaccine containing weakened versions of the four serotypes of the virus that cause dengue. 

WHO recommends the use of TAK-003 in children aged 6–16 years in settings with high dengue burden and transmission intensity. The vaccine should be administered in a 2-dose schedule with a 3-month interval between doses.  “The prequalification of TAK-003 is an important step in the expansion of global access to dengue vaccines, as it is now eligible for procurement by UN agencies including UNICEF and PAHO,” said Dr Rogerio Gaspar, WHO Director for Regulation and Prequalification.  “With only two dengue vaccines to date prequalified, we look forward to more vaccine developers coming forward for assessment, so that we can ensure vaccines reach all communities who need it.” The WHO prequalification list also includes CYD-TDV vaccine against dengue developed by Sanofi Pasteur.  Dengue is a vector-borne disease transmitted by the bite of an infected mosquito. Severe dengue is a potentially lethal complication which can develop from dengue infections.  It is estimated that there are over 100-400 million cases of dengue worldwide each year and 3.8 billion people living in dengue endemic countries, most of which are in Asia, Africa, and the Americas. The largest number of dengue cases reported was in 2023 with the WHO Region of the Americas reporting 4.5 million cases and 2300 deaths. Dengue cases are likely to increase and expand geographically due to climate change and urbanization.

The vaccine, designed to prevent harmful mutations, is seen as key to eradicating polio. A vaccine against a type of polio that is spreading in the Southern Hemisphere is expected to receive emergency approval before the end of the year. If it does, it will be the first time the World Health Organization has steered an unlicensed vaccine or drug through its emergency listing process. Wild polio has been almost eradicated. Only two countries — Afghanistan and Pakistan — still report cases. But a version of the virus that arose naturally from the weakened polio virus used in vaccination is increasing. What is called circulating vaccine-derived poliovirus (cVDPV) is increasing in both Afghanistan and Pakistan, as well as in the Philippines, Malaysia, Yemen and 19 African countries — with Chad, the Democratic Republic of the Congo and Côte d’Ivoire the worst affected in Africa.

So far in 2020, there have been more than 460 cases of vaccine-derived polio worldwide. This is more than 4 times the number detected by this time in 2019, which is a major problem for the 32-year, US$17-billion global campaign to wipe out the disease. Researchers who model polio infections say that for every known case, there are about 2,000 infections in the population. “Millions of people potentially have no immunity to the vaccine-derived virus, and that’s why we’re very concerned,” says Kathleen O’Reilly, an epidemiologist at the London School of Hygiene and Tropical Medicine who models polio infections. Independent scientific advisers to the World Health Organization (WHO) have been assessing a vaccine that is designed specifically to protect against cVDPV. This vaccine, a decade in the making, has been tested for safety and efficacy, but is not yet licensed and still has to undergo further trials. The WHO is in the last stages of considering whether to approve it more quickly, under what is called an emergency-use listing — a procedure that was created during the 2014–16 Ebola outbreak in West Africa, and which the agency is also preparing to use for coronavirus vaccines...

Published in Nature (Oct. 29, 2020):

https://doi.org/10.1038/d41586-020-03045-2

January 26, 2021 - The WHO Strategic Advisory Group of Experts (SAGE) on Immunization has issued Interim recommendations for use of the Moderna mRNA-1273 vaccine against COVID-19 in people aged 18 years and older. Here is what you need to know.Here is what you need to know.

Who should be vaccinated first?

As with all COVID-19 vaccines, health workers at high risk of exposure and older people should be prioritized for vaccination. As more vaccine becomes available, additional priority groups should be vaccinated, with attention to people disproportionately affected by COVID-19 or who face health inequities.

Who else can take the vaccine?

The vaccine is safe and effective in people with known medical conditions associated with increased risk of severe disease, such as hypertension, diabetes, asthma, pulmonary, liver or kidney disease, as well as chronic infections that are stable and controlled. Although further studies are required for immunocompromised persons, people in this category who are part of a group recommended for vaccination may be vaccinated after receiving information and counselling.
Persons living with HIV are at higher risk of severe COVID-19 disease. Known HIV-positive vaccine recipients should be provided with information and counselling. Vaccination can be offered to people who have had COVID-19 in the past. But individuals may wish to defer their own COVID-19 vaccination for up to six months from the time of SARS-CoV-2 infection. The vaccine can be offered to a breastfeeding woman who is part of a group recommended for vaccination (e.g. health workers); discontinuing breastfeeding after vaccination is currently not recommended.

Who should not take the vaccine?

While pregnancy puts women at a higher risk of severe COVID-19, the use of this vaccine in pregnant women is currently not recommended, unless they are at risk of high exposure (e.g. health workers). Individuals with a history of severe allergic reaction to any component of the vaccine should not take this or any other mRNA vaccine. While vaccination is recommended for older persons due to the high risk of severe COVID-19 and death, very frail older persons with an anticipated life expectancy of less than 3 months should be individually assessed. The vaccine should not be administered to persons younger than 18 years of age pending the results of further studies.

What’s the recommended dosage?

SAGE recommends the use of the Moderna mRNA-1273 vaccine at a schedule of two doses (100 µg, 0.5 ml each) 28 days apart. If necessary, the interval between the doses may be extended to 42 days. Compliance with the full schedule is recommended and the same product should be used for both doses.

Is it safe?

While this vaccine has yet to be approved by WHO for an Emergency Use Listing, it has undergone review by the European Medical Agency (EMA) and consequently meets WHO’s criteria for SAGE consideration. The EMA has thoroughly assessed the data on the quality, safety and efficacy of the Moderna COVID-19 vaccine and authorized its use across the European Union.
SAGE recommends that all vaccinees be observed for at least 15 minutes after vaccination. Those who experience an immediate severe allergic reaction to the first dose should not receive additional doses. Longer-term safety assessment involves continued follow up of clinical trial participants, as well as specific studies and continued surveillance of secondary effects or adverse events of those being vaccinated in the roll out. The Global Advisory Committee on Vaccine Safety, a group of experts that provides independent and authoritative guidance to the WHO on the topic of safe vaccine use, receives and assesses reports of suspected safety events of potentially international impact. 

How efficacious is the vaccine?

The Moderna vaccine has been shown to have an efficacy of approximately 92 per cent in protecting against COVID-19, starting 14 days after the first dose.

Does it work against new variants?

Based on the evidence so far, the new variants of SARS-CoV-2, including the B.1.1.7 and the 501Y.V2, do not alter the effectiveness of the Moderna mRNA vaccine. The monitoring, collection and analysis of data on new variants and their impact on the effectiveness of COVID-19 diagnostics, treatments and vaccines continues.

Does it prevent infection and transmission?

We do not know whether the vaccine will prevent infection and protect against onward transmission. Immunity persists for several months, but the full duration is not yet known. These important questions are being studied. In the meantime, we must maintain public health measures that work: masking, physical distancing, handwashing, respiratory and cough hygiene, avoiding crowds, and ensuring good ventilation.