After a primary infection, IgG reaches peak levels in the blood after 14–21 days. In subsequent re-infections, levels peak earlier and the titres are usually higher. Both IgG and IgM provide protective immunity to the infecting serotype of the virus. In testing for IgG and IgM antibodies there may be cross-reactivity with other flaviviruses which may result in a false positive after recent infections or vaccinations with yellow fever virus or Japanese encephalitis. The detection of IgG alone is not considered diagnostic unless blood samples are collected 14 days apart and a greater than fourfold increase in levels of specific IgG is detected. In a person with symptoms, the detection of IgM is considered diagnostic. Prevention Prevention depends on control of and protection from the bites of the mosquito that transmits it. The World Health Organization recommends an Integrated Vector Control program consisting of five elements: Advocacy, social mobilization and legislation to ensure that public health bodies and communities are strengthened; Collaboration between the health and other sectors (public and private); An integrated approach to disease control to maximize the use of resources; Evidence-based decision making to ensure any interventions are targeted appropriately; and Capacity-building to ensure an adequate response to the local situation. The primary method of controlling A. aegypti is by eliminating its habitats. This is done by getting rid of open sources of water, or if this is not possible, by adding insecticides or biological control agents to these areas. Generalized spraying with organophosphate or pyrethroid insecticides, while sometimes done, is not thought to be effective. Reducing open collections of water through environmental modification is the preferred method of control, given the concerns of negative health effects from insecticides and greater logistical difficulties with control agents. People can prevent mosquito bites by wearing clothing that fully covers the skin, using mosquito netting while resting, and/or the application of insect repellent (DEET being the most effective). While these measures can be an effective means of reducing an individual's risk of exposure, they do little in terms of mitigating the frequency of outbreaks, which appear to be on the rise in some areas, probably due to urbanization increasing the habitat of A. aegypti. The range of the disease also appears to be expanding possibly due to climate change. Vaccine In 2016 a partially effective vaccine for dengue fever became commercially available in the Philippines and Indonesia. It has been