First things first — no vaccination, herb, supplement is absolutely safe for every person. To get approved for use, a vaccinated persons must have better outcomes (as a group) than an unvaccinated person. I am of the early vaccinated generation. A class mate got Polio as a child recovered, and then later in life developed  Post-Polio syndrome. I got the Polio shots and was fine. A vaccine for whopping cough was not available when I was born, I got it and suffered some brain damage to my speech center. I once met someone my age that suffered major brain damage after whopping cough. Taking a shot for whopping cough has much less risk of life long adverse effects than getting it. I am pro-vaccination, being of the generation that saw disease after disease ripple through the population causing much harm. I do not want those times to return…..

Your Microbiome determines how effective the Vaccine is

• Antibiotics-driven gut microbiome perturbation alters immunity to vaccines in humans [2019]
• “the abundance of Prevotella copri and two Megamonas species were enriched in individuals with fewer adverse events” [2021]
• “Bifidobacterium adolescentis was enriched in high-responders while Bacteroides vulgatus, Bacteroides thetaiotaomicron and Ruminococcus gnavus were more abundant in low-responders ” [2021]
• “At 1 month after second dose of vaccination, seven species including B. adolescentis, A. equolifaciens and A. celatus were more abundant whereas B. vulgatus remained less abundant in high responders” [2021]
• Lactobacillaceae, Rumen family, and Clostridium bacteria were associated with vaccine efficacy [2021]
• The abundance of Clostridium and Lactonemae was positively correlated with vaccine efficacy [2020]
• “Of the species altered following vaccination, 79.4% and 42.0% in the CoronaVac and BNT162b2 groups, respectively, recovered at 6 months.” [2023]
• “Bilophila abundance was associated with better serological response, while Streptococcus was associated with poorer response.'[2023]
• “vaccination can also change the composition of the gut microbiome. We found that 1 month after a second vaccine dose, the relative abundances of Bacteroides caccae increased significantly” [2023]
• “This study demonstrated a statistically significant reduction in alpha diversity and a shift in gut microbiota composition following vaccination, characterised by reductions in Actinobacteriota, Blautia, Dorea, Adlercreutzia, Asacchaobacter, Coprococcus, Streptococcus, Collinsella and Ruminococcus spp and an increase in Bacteroides cacaae and Alistipes shahii. ” [2022]
• “Bifidobacterium and Faecalibacterium appeared to be microbial markers of individuals with higher spike IgG titers, while Cloacibacillus was associated with low spike IgG titers. ” [2023]
• “vaccine responders were associated with an increased abundance of Streptococcus Bovis and decreased abundance of Bacteroides phylum;’ [2017]
• “Responders were associated with increased Streptococcus Bovis abundance and decreased Bacteroides phylum abundance” [2018]
• “Proteus and Egella abundance were positively correlated with vaccine efficacy, and Fusobacterium and Enterobacteriaceae were negatively correlated with vaccine efficacy” [2020]
• “The abundance of Bifidobacterium longum subspecies was positively correlated ; Clostridium, Enterobacteriaceae, and Pseudomonas abundance were inversely correlated with vaccine efficacy [2019]

The Specific Vaccine and Your Microbiome

It is possible that the microbiome alteration caused by a vaccination will interact with an existing microbiome dysbiosis and cause adverse effects. The adverse effect could move the microbiome into a stable and more severe dysbiosis — the claims of a child developing autism after a vaccination is viable. The vaccination may be just a contributing cause to an existing disposition. The literature below suggests that there is no statistically significant evidence supporting some people beliefs.

A 2024 study found “Rates of early childhood vaccine receipt did not differ between autistic and non-autistic cohorts.” as well as “Notice of Retraction: Measles, Mumps, Rubella Vaccination and Autism” indicating early studies claiming association was questionable, if not outright ideological. “At the same time, other environmental factors, such as vaccination, maternal smoking, or alcohol consumption, are not linked to the risk of ASD. ” [2024]