A Tobacco plant (Nicotiana benthamiana) is pictured in a laboratory of the company Icon Genetic in Halle, August 14, 2014. Icon Genetics develop a technology to mass produce Ebola vaccine with the help of tobacco plants. REUTERS/Axel Schmidt (GERMANY - Tags: HEALTH SCIENCE TECHNOLOGY)

A boy receives polio vaccine drops in an outskirt of the Yemeni capital Sanaa August 11, 2014. Yemen's Ministry of Public Health and Population launched a national house-to-house polio immunization campaign on Monday, state media reported. REUTERS/Khaled Abdullah (YEMEN - Tags: HEALTH) 

A health worker administers drops of polio vaccine to children in an outskirt of the Yemeni capital Sanaa April 7, 2014. Yemen's Ministry of Public Health and Population launched a national polio immunization campaign on Monday, according to World Health Organization (WHO). REUTERS/Khaled Abdullah (YEMEN - Tags: HEALTH POLITICS) 

An Afghan child receives polio vaccination drops during an anti-polio campaign in Kabul March 24, 2014. REUTERS/Mohammad Ismail (AFGHANISTAN - Tags: HEALTH SOCIETY TPX IMAGES OF THE DAY) 

Displaced South Sudanese people administer oral cholera vaccines to themselves in a camp for internally displaced people in the United Nations Mission in South Sudan (UNMISS) compound in Tomping, Juba February 28, 2014. REUTERS/Andreea Campeanu (SOUTH SUDAN - Tags: CIVIL UNREST POLITICS HEALTH) 

A Palestinian boy receives polio vaccine at a hospital in Khan Younis in the southern of Gaza Strip February 23, 2014. REUTERS/Ibraheem Abu Mustafa (GAZA - Tags: HEALTH) 

A child receives polio vaccination during an anti-polio campaign on the outskirts of Jalalabad, January 26, 2014. REUTERS/Parwiz(AFGHANISTAN - Tags: HEALTH SOCIETY) 

A child receives polio vaccination during an anti-polio campaign on the outskirts of Jalalabad, January 26, 2014. REUTERS/Parwiz (AFGHANISTAN - Tags: HEALTH SOCIETY) 

A veterinarian from Taipei City Animal Protection Office prepares a rabies vaccine at a park in Taipei July 30, 2013. A total of 14 wild Formosan ferret-badgers have been found to be infected with rabies in Taiwan causing the government to urge people to vaccinate their pets in an effort to prevent the spread of the fatal disease, which has re-emerged in Taiwan after more than 50 years, reported local media. REUTERS/Pichi Chuang (TAIWAN - Tags: ANIMALS SOCIETY HEALTH) 

A dog is vaccinated by a veterinarian from Taipei City Animal Protection Office at a park in Taipei July 30, 2013. A total of 14 wild Formosan ferret-badgers have been found to be infected with rabies in Taiwan causing the government to urge people to vaccinate their pets in an effort to prevent the spread of the fatal disease, which has re-emerged in Taiwan after more than 50 years, reported local media. REUTERS/Pichi Chuang (TAIWAN - Tags: ANIMALS SOCIETY HEALTH) 

A dog is vaccinated by veterinarians from Taipei City Animal Protection Office at a park in Taipei July 30, 2013. A total of 14 wild Formosan ferret-badgers have been found to be infected with rabies in Taiwan causing the government to urge people to vaccinate their pets in an effort to prevent the spread of the fatal disease, which has re-emerged in Taiwan after more than 50 years, reported local media. REUTERS/Pichi Chuang (TAIWAN - Tags: ANIMALS HEALTH SOCIETY) 

Bottles of rabies vaccine are held while veterinarians from Taipei City Animal Protection Office prepare to vaccinate pet animals at a park in Taipei July 30, 2013. A total of 14 wild Formosan ferret-badgers have been found to be infected with rabies in Taiwan causing the government to urge people to vaccinate their pets in an effort to prevent the spread of the fatal disease, which has re-emerged in Taiwan after more than 50 years, reported local media. REUTERS/Pichi Chuang (TAIWAN - Tags: ANIMALS SOCIETY HEALTH) 

A child receives an oral polio vaccine during an anti-polio campaign in Sanaa June 30, 2013. REUTERS/Khaled Abdullah (YEMEN - Tags: HEALTH SOCIETY) 

A child receives an oral polio vaccine during an anti-polio campaign in Sanaa June 30, 2013. REUTERS/Khaled Abdullah (YEMEN - Tags: HEALTH SOCIETY TPX IMAGES OF THE DAY) 

Macsen Scott-Ambler, aged seven months, is given an MMR injection by Sister Sian Owen at the Paediatric Outpatients department at Morriston Hospital in Swansea, south Wales April 6, 2013. Following an increase in the number of confirmed cases of a measles in south Wales, parents in the area were urged to vaccinate their children, and hospitals in the region opened drop-in clinics on Saturday, local media reported. REUTERS/Rebecca Naden (BRITAIN - Tags: SOCIETY HEALTH) 

A doctor prepares an MMR injection in the Paediatric Outpatients department at Morriston Hospital in Swansea, south Wales April 6, 2013. Following an increase in the number of confirmed cases of a measles in south Wales, parents in the area were urged to vaccinate their children, and hospitals in the region opened drop-in clinics on Saturday, local media reported. REUTERS/Rebecca Naden (BRITAIN - Tags: SOCIETY HEALTH) 

Kieran Elford, aged 13, is given an MMR injection by a qualified school nurse at the Paediatric Outpatients department at Morriston Hospital in Swansea, south Wales April 6, 2013. Following an increase in the number of confirmed cases of a measles in south Wales, parents in the area were urged to vaccinate their children, and hospitals in the region opened drop-in clinics on Saturday, local media reported. REUTERS/Rebecca Naden (BRITAIN - Tags: SOCIETY HEALTH) 

Bottles of adjuvants for use with the Pandemrix H1N1 flu vaccine are seen lined up during a vaccination programme in Schiedam in this November 23, 2009 file photo. Picture taken November 23, 2009 REUTERS/Jerry Lampen/Files (NETHERLANDS - Tags: DRUGS SOCIETY HEALTH SCIENCE TECHNOLOGY) 

French professor Erwann Loret works on samples of a vaccine against AIDS in his laboratory in Marseille January 29, 2013. Clinical trials of a vaccine against the AIDS virus (HIV-1) will begin in February in Marseille with forty-eight infected volunteers, the Public Assistance Hospitals of Marseille (AP-HM) announced today. REUTERS/Jean-Paul Pelissier (FRANCE - Tags: HEALTH) 

French professor Erwann Loret works on samples of a vaccine against AIDS in his laboratory in Marseille January 29, 2013. Clinical trials of a vaccine against the AIDS virus (HIV-1) will begin in February in Marseille with forty-eight infected volunteers, the Public Assistance Hospitals of Marseille (AP-HM) announced today. REUTERS/Jean-Paul Pelissier (FRANCE - Tags: HEALTH) 

Nurses prepare influenza vaccine injections during a flu shot clinic at Dorchester House, a health care clinic, in Boston, Massachusetts January 12, 2013. Influenza has officially reached epidemic proportions in the United States, with 7.3 percent of deaths last week caused by pneumonia and the flu, the U.S. Centers for Disease Control and Prevention said on January 11. REUTERS/Brian Snyder (UNITED STATES - Tags: HEALTH SOCIETY) 

Chihn Ha, eight year old, gets an influenza vaccine injection from nurse Nho Nguyen (R) during a flu shot clinic at Dorchester House, a health care clinic, in Boston, Massachusetts January 12, 2013. Influenza has officially reached epidemic proportions in the United States, with 7.3 percent of deaths last week caused by pneumonia and the flu, the U.S. Centers for Disease Control and Prevention said on January 11. REUTERS/Brian Snyder (UNITED STATES - Tags: HEALTH SOCIETY) 

Six-year-old Diego Sanson receives an influenza vaccine injection at Massachusetts General Hospital in Boston, Massachusetts January 10, 2013. With flu cases in this city up tenfold from last year, the mayor of Boston declared a public health emergency January 9 as authorities around the United States scrambled to cope with a rising number of patients. REUTERS/Brian Snyder (UNITED STATES - Tags: HEALTH SOCIETY) 

A female polio worker gives polio vaccine drops to a child in Lahore December 20, 2012. An alliance of Pakistani clerics will hold demonstrations across the country against the killings of polio eradication campaign workers, leaders said on Thursday, as the death toll from attacks this week rose to nine. REUTERS/Mohsin Raza (PAKISTAN - Tags: CIVIL UNREST HEALTH) 

A female polio worker gives polio vaccine drops to a child at Lady Reading hospital in Peshawar December 19, 2012. Three workers in a polio eradication campaign were shot in Pakistan on Wednesday, and two of them were killed, the latest in an unprecedented string of attacks over the past three days that has partially halted the U.N.-backed campaign. REUTERS/Fayaz Aziz (PAKISTAN - Tags: HEALTH) 

An Afghan child receives polio vaccination drops during an anti-polio campaign in Kabul November 19, 2012. REUTERS/Parwiz (AFGHANISTAN - Tags: HEALTH SOCIETY) 

A child receives a drop of polio vaccine at the United Nations High Commissioner for Refugees (UNHCR) supported Jalozai camp on the outskirts of Peshawar September 25, 2012. Polio attacks the central nervous system and can cause permanent paralysis within hours of infection. There is no cure for polio, but it can be prevented. A polio vaccine given in several doses can protect a child for life. Immunising the last children on earth is an expensive, business - not because the vaccine is costly (most are made by generic manufacturers and cost between 12 and 14 U.S. cents a dose), but because reaching people displaced by war and poverty requires vast operational logistics, time and human resources. Picture taken September 25, 2012. To match Insight POLIO-ERADICATION/ REUTERS/Fayaz Aziz (PAKISTAN - Tags: HEALTH SOCIETY) 

Six-month old Emilio Capone gets a vaccination at the clinic of paediatrician Thomas Fischbach in the western town of Solingen September 4, 2012. REUTERS/Ina Fassbender (GERMANY - Tags: BUSINESS EMPLOYMENT HEALTH) 

Six-month old Emilio Capone gets a vaccination at the clinic of paediatrician Thomas Fischbach in the western town of Solingen September 4, 2012. REUTERS/Ina Fassbender (GERMANY - Tags: BUSINESS EMPLOYMENT HEALTH) 

A nurse immunizes a young girl for measles at International Medical Corps' clinic in Gendrassa camp in Maban, Upper Nile State, South Sudan, on the border with Sudan, August 1, 2012. According to the International Medical Corps, an estimated 120,000 refugees have fled violence and hunger in Sudan into camps in South Sudan. Approximately 1,000 refugees were transferred on Wednesday from Jamman camp to the newly constructed Gendrassa camp, where they receive health screenings and vaccinations at International Medical Corps' clinic. International Medical Corps has been providing primary health care, nutrition, water, sanitation and hygiene services in South Sudan since 1994. REUTERS/Margaret Aguirre/International Medical Corps/Handout (SOUTH SUDAN - Tags: SOCIETY POLITICS CIVIL UNREST HEALTH) 

A newly born baby is given a vaccine at a maternity hospital on the occasion of "World Population Day" in Kolkata July 11, 2012. The world's population edged to 7 billion people in 2011, up from 2.5 billion since 1950. This year's World Population Day focuses on the theme of "Universal Access to Reproductive Health Services", according to the United Nations. REUTERS/Rupak De Chowdhuri (INDIA - Tags: HEALTH TPX IMAGES OF THE DAY) 

A boy cries as he receives a Polio vaccine shot in Sanaa June 11, 2012. Yemen began a three-day nationwide house-to-house immunization campaign on Monday. REUTERS/Khaled Abdullah (YEMEN - Tags: SOCIETY HEALTH) 

A girl cries as she receives a Polio vaccine shot in Sanaa June 11, 2012. Yemen began a three-day nationwide house-to-house immunization campaign on Monday. REUTERS/Khaled Abdullah (YEMEN - Tags: SOCIETY HEALTH) 

An infant receives a polio vaccine shot at a health centre in Tegucigalpa April 25, 2012. The Honduran Health Ministry on Wednesday began a nationwide campaign to vaccinate more than 1.4 million children against polio, hepatitis B, meningitis, rotavirus, pneumococcal infection, measles, rubella and mumps, local media reported. REUTERS/Jorge Cabrera (HONDURAS - Tags: HEALTH) 

An Afghan child receives polio drops in Jalalabad province April 22, 2012. REUTERS/Parwiz (AFGHANISTAN - Tags: SOCIETY HEALTH) 

A vial of vaccine against measles and rubella is seen at a health point in El Alto, in the outskirts of La Paz, April 15, 2012. Bolivian health officials will offer vaccinations to some 200, 000 children in the country, local media reported. REUTERS/David Mercado (BOLIVIA - Tags: HEALTH SOCIETY) 

A child receives polio drops during the polio eradication programme in the northern Indian city of Chandigarh February 19, 2012. The polio eradication programme in India aims to immunize every child under five years of age with the oral polio vaccine. REUTERS/Ajay Verma (INDIA - Tags: HEALTH SOCIETY) 

A man receives a dose of a trivalent vaccine (a three component vaccine) for seasonal flu, influenza A (H1N1) and N2H3 in a subway station in Mexico City January 25, 2012. People can receive free vaccine shots in public areas as local authorities have stepped up precautions during the winter season, according to local media. REUTERS/Henry Romero (MEXICO - Tags: HEALTH POLITICS) 

A woman receives a dose of a trivalent vaccine (a three component vaccine) for seasonal flu, influenza A (H1N1) and N2H3 in a subway station in Mexico City January 25, 2012. People can receive free vaccine shots in public areas as local authorities have stepped up precautions during the winter season, according to local media. REUTERS/Henry Romero (MEXICO - Tags: HEALTH POLITICS) 

A child receives a dose of polio vaccine for children under the age of five, during the first day of a national three-day campaign against polio in Sanaa November 14, 2011. REUTERS/Mohamed al-Sayaghi (YEMEN - Tags: HEALTH SOCIETY) 

A newly arrived Somali refugee child receives a polio drop at the Ifo extension refugee camp in Dadaab, near the Kenya-Somalia border, August 1, 2011. Aid agencies vaccinate against polio and measles in Kenya's Dadaab area where hundreds of thousands of refugees have settled after fleeing devastating drought and warfare in Somalia. REUTERS/Thomas Mukoya (KENYA - Tags: SOCIETY CIVIL UNREST DISASTER ENVIRONMENT) 

A nurse prepares a vaccine against the influenza A (H1N1) virus, or swine flu, in Caracas March 29, 2011. There are 415 reported cases of swine flu in people across the country, Venezuela's Health Minister Eugenia Sader said on Monday. REUTERS/Jorge Silva (VENEZUELA - Tags: ENVIRONMENT HEALTH) 

A child reacts as he receives a vaccination against the influenza A (H1N1) virus, or swine flu, in Caracas March 29, 2011. There are 415 reported cases of swine flu in people across the country, Venezuela's Health Minister Eugenia Sader said on Monday. REUTERS/Jorge Silva (VENEZUELA - Tags: ENVIRONMENT HEALTH IMAGES OF THE DAY) 

A team from UNICEF (Ivory Coast) vaccinates children against polio at St. Ambrose church in Angree, Abidjan March 9, 2011, a temporary refuge for people fleeing from clashes between forces loyal to incumbent leader Laurent Gbagbo and his rival Alassane Ouattara. REUTERS/Thierry Gouegnon (IVORY COAST - Tags: HEALTH SOCIETY) 

A member of UNICEF (Ivory Coast) fills a syringe during a vaccination campaign against polio at St. Ambrose church in Angree, Abidjan March 9, 2011, a temporary refuge for people fleeing from clashes between forces loyal to incumbent leader Laurent Gbagbo and his rival Alassane Ouattara. REUTERS/Thierry Gouegnon (IVORY COAST - Tags: HEALTH SOCIETY) 

A child is given an injection as part of a malaria vaccine trial at a clinic in the Kenya coastal town of Kilifi, November 23, 2010. Malaria threatens half the people on the planet and kills around 800,000 people a year, many of them too young to have even learned to walk. The death rate has come down in the last decade, but full-scale eradication will cost billions and drag funds away from other equally, or possibly even more urgent health efforts. As governments in poor countries and donors from wealthy ones weigh up where to put their money, experts have begun a quiet but fundamental debate about whether wiping out malaria is realistic or even makes economic sense. Picture taken November 23, 2010. To match Special Report MALARIA/COST REUTERS/Joseph Okanga (KENYA - Tags: BUSINESS HEALTH) 

Lois Dama (2nd R) holds her baby daughter Rehema as she is given an injection as part of a malaria vaccine trial in the Kenya coastal town of Kilifi, November 23, 2010. Malaria threatens half the people on the planet and kills around 800,000 people a year, many of them too young to have even learned to walk. The death rate has come down in the last decade, but full-scale eradication will cost billions and drag funds away from other equally, or possibly even more urgent health efforts. As governments in poor countries and donors from wealthy ones weigh up where to put their money, experts have begun a quiet but fundamental debate about whether wiping out malaria is realistic or even makes economic sense. Picture taken November 23, 2010. To match Special Report MALARIA/COST REUTERS/Joseph Okanga (KENYA - Tags: BUSINESS HEALTH) 

A child cries as he is vaccinated against the most deadly forms of pneumonia at the Amistad Mexico-Nicaragua Hospital in Ticauntepe town, about 8 miles (13 kilometres) south of Managua, December 12, 2010. The Global Alliance for Vaccines and Immunisation (GAVI) said Nicaragua is the first developing nation to begin vaccinating children with the pneumococcal shots, made by drugmakers Pfizer and GlaxoSmithKline, and another 18 countries will follow in the next few years. Pneumococcal disease, which can cause pneumonia, meningitis and sepsis, kills more than half a million children every year and the vast majority of these deaths are in poorer countries where access to healthcare can be limited and very expensive. REUTERS/Oswaldo Rivas(NICARAGUA - Tags: HEALTH BUSINESS) 

A girl is vaccinated in a homeless shelter at the headquarters of the Bolivarian National Police in the low-income neighbourhood of Catia in Caracas November 29, 2010. Heavy rains in the past few days have caused floods and landslides in the slums of Caracas on Saturday, according to the local media. REUTERS/Carlos Garcia Rawlins (VENEZUELA - Tags: POLITICS DISASTER HEALTH) 

Veterinarians vaccinate a goose against bird flu in the village of Kaikovo, some 20 km (12 miles) south of Minsk, March 29, 2010. Poultry near ponds are vaccinated every spring before migrant birds arrive, a veterinary official said. REUTERS/Vasily Fedosenko (BELARUS - Tags: ANIMALS HEALTH ENVIRONMENT) 

A police officer prepares to receive a H1N1 flu vaccine injection at a patrol police station in the Siberian city of Krasnoyarsk March 25, 2010. Local authorities launched a vaccination campaign against the H1N1 flu among Interior Ministry members, local media reported. REUTERS/Ilya Naymushin (RUSSIA - Tags: HEALTH MILITARY) 

A nurse prepares a H1N1 influenza vaccine during the start of a campaign against the influenza at a hospital in Tegucigalpa March 23, 2010. There have been 18 deaths since the arrival of the virus in the country, according to Honduras Ministry of Health. REUTERS/Edgard Garrido (HONDURAS - Tags: HEALTH) 

A woman receives a H1N1 influenza vaccine shot from a medical staff at a hospital in Nonthaburi province, on the outskirts of Bangkok January 11, 2010. Thailand started the H1N1 vaccination programme on Monday to combat the deadly virus which killed 192 people in the country. Some two million doses of the vaccine were imported from France to be handed out to high-risk groups during the programme, health officials said. REUTERS/Chaiwat Subprasom (THAILAND - Tags: HEALTH) 

Boonya Klaer-orm, 25, who is 8 months pregnant, receives a H1N1 influenza vaccine shot from a medical staff at a hospital in Nonthaburi province, on the outskirts of Bangkok January 11, 2010. Thailand started the H1N1 vaccination programme on Monday to combat the deadly virus which killed 192 people in the country. Some two million doses of the vaccine were imported from France to be handed out to high-risk groups during the programme, health officials said. REUTERS/Chaiwat Subprasom (THAILAND - Tags: HEALTH) 

A medical assistant holds up a H1N1 flu vaccine at a hospital in Belgrade December 17, 2009. Serbia on Thursday started a vaccination programme for patients and workers most at risk. REUTERS/Djordje Kojadinovic (SERBIA - Tags: HEALTH) 

A bio-reactor is seen located in the area where cells will be infected with the flu virus in the process of manufacturing vaccines at the Novartis facility in Holly Springs, North Carolina, November 24, 2009. The facility, which officially opened Tuesday, is the first large scale flu cell culture and adjuvant manufacturing facility in the United States. It will have the capability to produce seasonal flu cell culture vaccine, pre-pandemic vaccine and 150 million doses of pandemic vaccine within six months of an influenza pandemic declaration. REUTERS/Jason Arthurs (UNITED STATES BUSINESS SOCIETY HEALTH) 

Makayla Fofu, 4, screams while her mother Abena holds her as a nurse injects a shot of the H1N1 flu vaccine, in Arlington, Texas November 24, 2009. REUTERS/Jessica Rinaldi (UNITED STATES HEALTH SOCIETY)