(DTP) vaccination was licensed in 1949. Since the introduction of the combination vaccine, there has been an extensive decline in the incidence of pertussis, or whooping cough, the disease which the vaccine protects against. Additionally, the rates of disease have continued to decline as more extensive immunization strategies have been implemented, including booster doses and increased emphasis on increasing health literacy. Vaccination Rates In 2016, the CDC reported that 80.4% of children in the US have received four or more DTaP vaccinations by 2 years of life. Vaccination rates for children aged 13–17 with one or more TDaP shots was 90.2% in 2019. Only 43.6% of adults (older than 18) have received a TDaP shot in the last 10 years. The CDC aims to increase vaccination rate among 2-year-olds from 80.4% to 90.0% Combination vaccines with acellular pertussis DTaP and Tdap are both combination vaccines against diphtheria, tetanus, and pertussis. The lower-case "d" and "p" indicate smaller concentrations of diphtheria toxoids and pertussis antigens, and "a" in "ap/aP" indicates that the pertussis toxoids are acellular. DTaP DTaP (also DTPa and TDaP) is a combination vaccine against diphtheria, tetanus, and pertussis, in which the pertussis component is acellular. This is in contrast to whole-cell, inactivated DTP (DTwP). The acellular vaccine uses selected antigens of the pertussis pathogen to induce immunity. Because it uses fewer antigens than the whole-cell vaccines, it is considered to cause fewer side effects, but it is also more expensive. Research suggests that the DTP vaccine is more effective than DTaP in conferring immunity, because DTaP's narrower antigen base is less effective against current pathogen strains. Tdap Tdap, (also dTpa), is a tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine. It was licensed in the United States for use in adults and adolescents on 10 June 2005. Two Tdap vaccines are available in the US. In January 2011, the US Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) recommended the use of Tdap in adults of all ages, including those age 65 and above. In October 2011, in an effort to reduce the burden of pertussis in infants, the ACIP recommended that unvaccinated pregnant women receive a dose of Tdap. On 24 October 2012, the ACIP voted to recommend the use of Tdap during every pregnancy. The ACIP and Canada's National Advisory Committee on Immunization (NACI) recommended that both adolescents and adults