(D) If an infection by the same pathogen occurs in the future, the immune system already has antibodies at the ready.
The body can rapidly recognize the pathogen based on its antigen and launch a fast, effective defense.
From my perspective the antivaxxer movement is growing in strength and momentum.
In order to counter allegations that vaccines could cause autism, it is both useful and informative to have access to some key recent scientific literature. Peter Hotez MD Ph D is professor of pediatrics and molecular virology and microbiology at Baylor College of Medicine, where is also Texas Children’s Hospital Endowed Chair in Tropical Pediatrics, and Dean of the National School of Tropical Medicine.
Today, anti-vaccinationists (sometimes known as “anti-vaxxers”), who include parents, politicians, religious leaders, and more, strongly oppose vaccination, particularly childhood vaccination.
At its core, the anti-vaccination movement argues that vaccines are unnecessary, ineffective, or dangerous. A closer look at the evidence surrounding vaccinationists suggests that while the anti-vaccinationist ideals are compelling, a more accurate picture of vaccination may be found elsewhere. This study does not support the hypothesis that thimerosal-containing vaccines and/or the MMR vaccine play a role in the etiology of autism”.Taken together these studies show that childhood or maternal vaccines do not cause autism.Ever since the first vaccination was scientifically documented in 1798 , they have reshaped the landscape of human health and medicine. The impacts of vaccines have ranged from the 1979 eradication of polio in the US  and the 1980 eradication of smallpox worldwide , to prevention of cancer of the liver  and the cervix . I also point out that the lack of plausibility of any link between childhood vaccines and autism.Numerous studies indicate that autism is associated with changes neocortex of the brain in early pregnancy well before a child receives vaccines.Importantly, a vaccine protects not only the individual to whom it is administered, but also the entire population. When the number of immunized individuals within a population reaches a critical threshold, herd immunity  is conferred (Figure 2). According to the paper summary: “Here we gave nonhuman primate infants similar vaccines given to human infants to determine whether the animals exhibited behavioral and/or neuropathological changes characteristic of autism.No behavioral changes were observed in the vaccinated animals, nor were there neuropathological changes in the cerebellum, hippocampus, or amygdala.