Understand why some vaccines are only given in childhood, adolescence, adulthood or elderly
by Butantan Team
Published: November 26, 2021
The World Health Organization (WHO) is the main guide of the vaccination calendar, but it is the countries that decide, according to their economic and epidemiological capacity, which immunizers are included in their annual vaccination campaigns. In Brazil, there are different vaccines for each public: children, adolescents, adults and the elderly. This is because vaccines were developed, over decades of study, for the target audience in which the incidence of each disease is higher.
The triple bacterial, which fights tetanus, diphtheria and pertussis, is given to children because the main risk group for pertussis are children under five. The older ones only take the adult pair every ten years, for tetanus and diphtheria, without the whooping cough. This is because if a person had a complete vaccination as a child, pertussis will not be a serious problem for the adult body. As it has a much lower incidence in the adult population, the disease is no longer epidemiologically relevant.
Until recently, the yellow fever vaccine required a booster dose every ten years. Recently, the WHO realized that a fifth of the dose is as effective as the full dose, and eliminated the need for a decade booster for those taking the full dose. But this does not mean that increasing a dosage helps the immune system to fight the disease all at once. When the vaccine is developed, one of the things that is studied is the dose escalation.
“If the result shows that 20 milligrams or 100 milligrams already immunizes, then there is no need to waste antigen for nothing. I use the 20 milligrams, which solves it. It’s called the plateau”, says the scientific researcher and director of the vaccine development laboratory, Viviane Maimoni Gonçalves.
The maturity of the immune system also plays an important role in distributing the vaccine schedule. As people get older, the immune system, because of immunosenescence (immunological changes seen in aging), does not respond as well, unlike the immunocompetent adult.
The disease often has an incidence in a certain population, but it has no clinical relevance or severity. The BCG vaccine (Bacille Calmette-Guerin, which prevents severe forms of tuberculosis, especially miliary and meningeal), for example, is not able to prevent tuberculosis in an adult, but it does prevent the severe form of the disease in babies. In an older person, TB needs to be treated with medication until an effective vaccine is developed for this age group.
“We see that these groups often go together, the elderly and babies. In one the immune system is not yet mature enough to deal with a series of pathogens and in the other the immune system is already aging”, explains Viviane. The flu vaccination, for the elderly and children, is annual. The little ones are vaccinated from six months to six years of age – after that age, it is understood that the disease is not as clinically relevant.
Many diseases disappeared because there was a worldwide vaccination effort organized by the WHO, as in the case of smallpox – the last case was identified in the 1970s. For Viviane, the best strategy is always to vaccinate all stakeholders as soon as possible.
“Brazil has not had any case of poliomyelitis (child paralysis) since 1989, but the authorities are concerned because vaccination coverage, which is the most tranquil, that of the droplet, has dropped a lot. If there is an introduction of polio in Brazil, we could have an outbreak”, she says
Another example is measles. Brazil was free of the disease for a long time, but as vaccination coverage dropped, it returned to haunt.
“People need to understand that the action of the vaccine is collective, not individual. The entire population has to be vaccinated and it is our responsibility to protect those who are on our side, who are more susceptible, or those who cannot be vaccinated”, explains Viviane. Measles can kill or have serious consequences in adults – that’s why vaccination is so important.
Vaccines for all ages
The Ministry of Health’s National Vaccination Calendar provides 15 vaccines for more than 20 types of diseases, and immunization begins in the first weeks of life.
Before the first month, the baby must be vaccinated with BCG and the first dose of hepatitis B. At two months, he should receive penta (which prevents diphtheria, tetanus, whooping cough, hepatitis B and infections caused by Haemophilus influenzae B), inactive polio vaccine (VIP), 10-valent pneumococcal vaccine (which prevents pneumonia, otitis, meningitis and other diseases caused by pneumococcus) and against rotavirus.
At three months, meningococcal C is applied. At four months, comes the second dose of penta, VIP, pneumococcal and rotavirus. And, at five months, the second dose of meningococcal C.
At six months, the baby should take the third dose of the penta and VIP. Upon completing nine months, he has the yellow fever vaccine available.
At one year of age comes the MMR (which prevents measles, mumps, and rubella), and the 10-valent pneumococcal and meningococcal C boosters.
At 15 months, the child should receive DTP (which prevents diphtheria, tetanus and whooping cough), oral polio vaccine (VOP), hepatitis A and tetra viral (which prevents measles, rubella, mumps and chickenpox/pox).
At four years of age, the child receives DTP and VOP boosters, in addition to a second dose of attenuated chickenpox.
Children ages six months to five years of age should also get one or two doses of influenza vaccine during the Annual Influenza Vaccination Campaign.
Entering adolescence, girls and boys up to 14 years of age should receive the HPV vaccine (which prevents human papillomavirus, which causes cancers and genital warts) and also meningococcal C.
From ten to 19 years old, hepatitis B, yellow fever, adult double and triple viral vaccines are recommended. From 20 to 59, adults get hepatitis B, yellow fever, adult double and triple viral.
After age 60, hepatitis B, yellow fever, dual adult, influenza (annual) and 23-valent pneumococcal (which prevents pneumonia, otitis, meningitis, and other diseases caused by pneumococcus) vaccines are needed.
There is also a calendar for pregnant women, with three doses of hepatitis B, three double adult doses, and one triple bacterial and influenza dose.