Have we forgotten about smallpox? Wasn’t that a pandemic? Wasn’t a vaccine used? Didn’t the vaccine not only eradicate the pandemic but even the virus all together?
A pandemic is not necessarily characterized by waves. In cases of a viral pandemic, waves only occur with pandemics of acute self-limiting viral infections (ASLVIs) caused by glycosylated viruses. This is the only case where waves are not only required but also sufficient to generate herd immunity. That process is rooted in the natural immune response acquired by individuals who experienced productive viral infection. Smallpox, however, does not cause ASLV infection but acute, self-limiting viral disease(ASLVD). A pandemic of smallpox in a given place/ country doesn’t come in waves and, therefore, herd immunity (HI) cannot be generated (see below). In case of smallpox, generation of herd protection is rooted in the natural immunity acquired by each individual who experienced and abrogated the disease. That type of immunity is not prone to immune escape since abrogation of viral infection is based on elimination of virus-infected host cells by MHC-unrestricted, polyspecific T cells. Hence, you can mimic this with any live attenuated poxvirus (as the CTL epitope is highly conserved). As this response will be memorized upon re-exposure, the population will be fully protected against any poxvirus coming along (you eradicate the virus by making the population resistant to productive infection).
So, at least for viruses causing ASLVD, like poxviruses, there is clear evidence that society vaccinated its way out of a pandemic.
Howevern it is impossible to do this with ASLVI (caused by other glycosylated viruses); this is because natural immunity in this case is based on a well-orchestrated collaborative effort of trained innate immune cells (NK cells) and acquired antigen-specific antibodies (Abs) [so, not on elimination of virus-infected cells only!]. Herd protection in this case relies on prevention (not abrogation!) of (productive) infection. In case of high infectious pressure (pandemic/ epidemic!), this will definitely require the support from the acquired Ag-specific Abs. That’s where the issue of ‘immune escape’ comes up: Abs generated as a result of mass vaccination, even using live attenuated virus (like in the case of smallpox), will not be able to rapidly and sufficiently support innate immune cells to get rid of the viral load. This particularly occurs in the elderly (or vulnerable) population due to weakened innate immunity. It creates a situation where growing titers of immature Ab titers are regularly encountering a high viral load: A recipe for immune escape! So even upon using live viral vaccines it’s impossible to vaccinate you way out of a pandemic of a glycosylated virus causing ASLVI.
Only a pandemic of a glycosylated virus causing ASLVI can generate herd protection via herd immunity. However, it’s only possible for Nature (all my respect!) to do this if the fight (between virus and host immune system) get split up in several stages (so called ‘waves’ of the pandemic). After each stage/ wave, herd immunity has grown and will finally reach a stage where the level of trained innate immunity in the population is strong enough to diminish viral transmission down to a level where the Abs don’t drive any longer natural selection and adaptation of more infectious immune escape variants; that’s how the threshold of HI is achieved without driving immune escape . Of course, HI isn’t sterilizing and does not enable eradication of the virus. So, asymptomatic infection and transmission will still occur and characterize the endemic phase….A nice equilibrium that satisfies both the virus (can still replicate) and the population (no longer suffering from disease and death) and that will limit a flare-up to an outbreak, not to an epidemic (unless natural ‘antigenic shift’ or antigenic shift driven by a mass vaccination program conducted in the midst of a pandemic!)
Hope this shows once again that the answer to all these Qs lies in the science.
Geert Vanden Bossche received his DVM from the University of Ghent, Belgium, and his PhD degree in Virology from the University of Hohenheim, Germany. He held adjunct faculty appointments at universities in Belgium and Germany. After his career in Academia, Geert joined several vaccine companies (GSK Biologicals, Novartis Vaccines, Solvay Biologicals) to serve various roles in vaccine R&D as well as in late vaccine development.
Geert then moved on to join the Bill & Melinda Gates Foundation’s Global Health Discovery team in Seattle (USA) as Senior Program Officer; he then worked with the Global Alliance for Vaccines and Immunization (GAVI) in Geneva as Senior Ebola Program Manager. At GAVI he tracked efforts to develop an Ebola vaccine. He also represented GAVI in fora with other partners, including WHO, to review progress on the fight against Ebola and to build plans for global pandemic preparedness.
Back in 2015, Geert scrutinized and questioned the safety of the Ebola vaccine that was used in ring vaccination trials conducted by WHO in Guinea. His critical scientific analysis and report on the data published by WHO in the Lancet in 2015 was sent to all international health and regulatory authorities involved in the Ebola vaccination program. After working for GAVI, Geert joined the German Center for Infection Research in Cologne as Head of the Vaccine Development Office. He is at present primarily serving as a Biotech / Vaccine consultant while also conducting his own research on Natural Killer cell-based vaccines.
Email: info@voiceforscienceandsolidarity.org
.svg){kind=small}
