Phase 1 clinical trials assess the safety and dosage of a vaccine in a small number of people, typically a dozen to several dozen healthy volunteers. Clinical trials are studies that are typically conducted in three phases to assess the safety and efficacy of vaccines in increasingly larger numbers of volunteers. The safety and efficacy of a vaccine are determined through clinical trials. How do we know if a vaccine is safe and effective? This is one of the reasons why it will still be important for people to continue wearing masks and practicing physical distancing, even after being vaccinated. It is likely they reduce the risk of virus transmission but probably not completely in everyone. We are still learning whether or not the current Covid-19 vaccines prevent transmission of SARS-CoV-2. Many vaccines can also prevent transmission, potentially leading to herd protection whereby unvaccinated people are protected from infection by the vaccinated people around them because they have less chance of exposure to the virus. In general, most vaccines do not completely prevent infection but do prevent the infection from spreading within the body and from causing disease. These people have asymptomatic infection but can still transmit the virus to others. Not all people who are infected with SARS-CoV-2 develop disease (Covid-19 is the disease caused by the virus SARS-CoV-2). Blocking this entrance prevents infection. In this way, vaccines mimic natural infection but without actually causing the person to become sick.įor SARS-CoV-2, antibodies that bind to and block the spike protein on the virus’s surface are thought to be most important for protection from disease because the spike protein is what attaches to human cells, allowing the virus to enter our cells. ![]() Vaccines stimulate the human body’s own protective immune responses so that, if a person is infected with a pathogen, the immune system can quickly prevent the infection from spreading within the body and causing disease. Zoonotic and other diseases can also require an emergency response.International Vaccine Access Center How do vaccines work? ![]() Gastroenteritis - guidelines for investigation.The following food and water borne diseases can require an emergency response: untreated water contaminated by human faeces.foods contaminated by infected food handlers.raw or lightly cooked fish, shellfish or other seafood.The most frequent causes of food or water-borne illnesses are various bacteria, viruses and parasites. Ross River virus and Barmah Forest virusįood-related illness and water-borne diseases. ![]() The following vector-borne diseases can require an emergency response: Vector-borne diseases can be spread by mosquitoes, ticks, flies, sandflies, fleas, triatomine bugs and some freshwater aquatic snails. Vector-borne diseases occur when vectors (living organisms such as bloodsucking insects) transmit infectious diseases between humans or from animals to humans. Check the pandemic influenza page for more information about international, national and state plans to respond to pandemic influenza. Pandemic influenza can require an emergency response. During a pandemic, the virus spreads rapidly around the world causing high rates of illness and death and resulting in severe social and economic disruption. An influenza pandemic occurs when a highly infectious new strain of flu emerges for which humans have little or no immunity. Pandemic influenza and large-scale vector-borne diseases, food-related illness and water-borne diseases can require an emergency response. The spread of a communicable disease usually happens via airborne viruses or bacteria (for example, by coughs and sneezes), but disease can also spread through contact with blood or other bodily fluid. Infectious diseases are spread from one person to another, or from an animal to a person.
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