First, is the attenuated or live vaccines such as vaccinia(smallpox), varicella(chickenpox) and rotavirus. Second, we have the inactivated or killed vaccines, which include inactivated poliovirus(IPV), rabies and hepatitis A. Third, the toxoid vaccines mainly diphtheria, tetanus which is part of the DPT combined immunization. Fourth, the subunit vaccines such as Haemophilus influenza type b. Fifth, the conjugate vaccines include pneumococcal, human papillomavirus(HPV), and meningococcal. As stated by Bloom (2015), the design of a vaccine depends on how the agent causing the disease infects the cell and the response of the immune system to