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Beware of the Crocodiles
Published in Norman Begg, The Remarkable Story of Vaccines, 2023
Vaccine efficacy is easily misunderstood, as it is calculated based at a population level, not an individual level. The best way to think of the efficacy of a vaccine is that it is the percentage reduction in the risk of you catching a disease if you are vaccinated versus not being vaccinated. It’s also worth noting that the larger the size of the Phase 3 trial, the more accurate will be the estimate of efficacy that is calculated. As well as giving the efficacy result, there will be a range, showing the upper and lower estimate. The efficacy estimate is the most likely correct result, but the range tells you it might be as low as x or as high as y. This range is called the confidence interval (sometimes also known as the credible interval).
Neurological events following immunizations
Published in Avindra Nath, Joseph R. Berger, Clinical Neurovirology, 2020
There are several important determinants of vaccine efficacy, which modulate the intensity of peak antibody responses. The nature of the vaccine antigen and its intrinsic immunogenicity are important, with some antigens being inherently more immunogenic than others. Live vaccines generally elicit stronger innate immune responses and thus stronger antibody responses. Non-live vaccines frequently require the use of adjuvants, or agents which increase the stimulation of the immune system by enhancing antigen presentation; aluminum salts are frequently used as adjuvants [18]. Many vaccines, particularly inactivated vaccines, require multiple doses to induce high and sustained antibody responses, or may require repeated administration at particular intervals. Antibody persistence is critically important; for the vaccine immune response to last, memory B cells, which are capable of recognizing and responding to an antigen challenge and subsequently proliferating and differentiating into antibody producing plasma cells, must be produced. Antibody persistence may be dependent on several different determinants, including the nature of the vaccine (live vs. inactivated), interval between doses, and age at immunization.
Analysis of Vaccine Studies and Causal Inference
Published in Leonhard Held, Niel Hens, Philip O’Neill, Jacco Wallinga, Handbook of Infectious Disease Data Analysis, 2019
Neafsey et al. (2015) presented estimates of vaccine efficacy using both 1 minus the ratio (vaccine vs. control) of cumulative incidences and 1 minus the ratio (vaccine vs. control) of hazards, the latter under the assumption that the hazards are proportional over time. The context was to estimate the efficacy of the RTS,S/AS01 malaria vaccine according to genetic diversity of the parasite. The estimates of vaccine efficacy based on the two methods differ significantly in several of the analyses.
Lessons learned from the SARS-CoV-2 pandemic; from nucleic acid nanomedicines, to clinical trials, herd immunity, and the vaccination divide
Published in Expert Opinion on Drug Delivery, 2023
Hiba Hussain, Aishwarya Ganesh, Lara Milane, Mansoor Amiji
For Pfizer’s booster trials, participants were randomized in a 1:1 ratio to receive either the 30 µg booster dose (same as the primary vaccine course dosage strength) or the placebo. The median time between the second dose and administration of booster/placebo was around 11 months. The vaccine efficacy was found to be 95.6%, which reflected a reduction in disease occurrence in the booster cohort compared to the non-booster cohort (without prior SARS-CoV-2 infection). The vaccine efficacy was consistent across multiple subgroups regardless of age, sex, race, ethnicity, or comorbidity parameters. Johnson and Jonhson’s (JnJ’s) single shot demonstrated 79% effectiveness for COVID-19-related infections, and 81% effectiveness for COVID-19-related hospitalizations. Booster shots administered 56 days after the first shot provided a 75% protection against symptomatic (moderate to severe) COVID-19 globally. After administering the JnJ booster two months after the first shot, antibody levels increased 4–6-fold, while that given six months after the single shot elicited a nine-fold antibody increase a week after administration, and twelve-fold a month after administration. Boosters have clearly proven their effectiveness, however, the question remains, when will the need for boosters end?.
Severe mental disorders and vaccinations – a systematic review
Published in The World Journal of Biological Psychiatry, 2022
Nina Bonkat, Frederike T. Fellendorf, Nina Dalkner, Eva Z. Reininghaus
The purpose of vaccinations is to prevent severe, life-threatening infections such as pneumococcal disease, hepatitis B and tuberculosis. In December 2020, the first vaccines against the SARS-CoV-2 virus were approved. Vaccines influence the immune system mostly by stimulating the formation of antibodies, but can also evoke a T-cell response. Vaccine immunogenicity is the ability of a vaccine to elicit an immune response and can be determined by measuring antibody titres. In contrast, vaccine efficacy is the ability to protect the vaccinated individual from infection and can be measured by the risk reduction of infection in vaccinated individuals in a controlled clinical trial (Banaszkiewicz and Radzikowski 2013). However, it has been suggested that individuals with SMI have an impaired response to vaccinations influenced by their chronic pro-inflammatory profiles, as well as impaired adaptive immune systems. Additionally, efficacy and side effects of vaccinations might be different in individuals with SMI compared with the general population. Psychopharmacological treatment might also affect the response of vaccinations.
Tapping the immunological imprints to design chimeric SARS-CoV-2 vaccine for elderly population
Published in International Reviews of Immunology, 2022
Asim Biswas, Rahul Shubhra Mandal, Suparna Chakraborty, George Maiti
In addition to the appropriate selection of adjuvants and suitable modification of antigens, vaccine efficacy largely depends on several host factors. Considering the weaken immune system of the elderly people and several other co-morbid clinical conditions, effective vaccination must overcome these hurdles successfully. An aged immune system harbors multitude of changes especially a steady decline in naïve CD4+ T cell number due to inability of lymphocyte generation in the primary lymphoid organ. Parallelly, alternation of secondary lymphoid structure and function results in altered T cell trafficking and a restricted T cell repertoire [16,106]. Depletion of naïve CD4+ T cells during vaccination in elderly people significantly reduces the vaccine efficacy. The influenza specific memory T cells are directed toward conserved protein sequences across numerous influenza strains available. Therefore, these memory T cells can successfully confer cross protection against numerous strains of influenza and strategically bestows an alternative approach to treat elderly people with an added advantage. Older individuals have encountered several influenza strains throughout their life span and unknowingly carries diverse influenza specific memory CD4+ T cell populations [107].