I was looking at the Robert F Kennedy Jr web site on vaccine - there is a link to a study on asymptomatic transmission of whooping cough and vaccines which saysIs there any data on children developing symptoms or remaining asymptomatic and which childhood vaccines they have or have not had?
Interesting vaccine article
Thanks for the above links, they were very helpful in giving me a better understanding and appreciation of the phenomenon of ADE, and how this might relate to the Sars-cov-2 vaccine efforts.There seems to be some conflicting info about ADE and covid-19 - the risks are not known particularly from infection by a new strain of covid-19 after vaccination against an earlier strain
The first article indicats why ADE maybe a risk and was seen in earlier MERS animal studies. The second older link says ADE was not seen in limited covid-19 animal trials from April 2020
Dengue Fever, COVID ‐19 (SARS‐CoV ‐2), and Antibody‐Dependent Enhancement (ADE ): A Perspective: 07 June 2020
The link below works
In summary, in both SARS‐CoV and MERS‐CoV infected anti‐spike S‐protein NAbs are present. They can induce experimentally in vitro and in vivo ADE mediated by FcγRII receptor virus entry. Previous immunization by vaccination or infection might aggravate symptoms of a follow‐up infection as described above for dengue fever, such complications were also observed for common influence and other viral infections (24).
Are there indications that ADE might be relevant in the SARS‐CoV‐2 pandemic? By nature, at this time point, trustworthy proofs for ADE playing clinically a role are not available and might be expected earliest in fall of 2020. Even so, the potential threat of ADE has to be investigated more closely, particularly in view of the vast number of recovered individuals who have already developed immunity. Thus, ADE is of relevance for the strategies for vaccine development and therapeutic agents. For example, ADE can play a role in individuals with immunity and NAbs against strain A if the next infection is by RBD mutated strain B. Antistrain A NAbs may not neutralize strain B, or antibody titers are too low for sufficient neutralization, or NAbs have efficient neutralizing capabilities, but cell entry occurs via FcγRII into APCs or B cells (43) (see Fig. 1).
This article mentions ADE has so far not been seen in animal testing
Thanks for the above links, they were very helpful in giving me a better understanding and appreciation of the phenomenon of ADE, and how this might relate to the Sars-cov-2 vaccine efforts.
Subsequent to the publication of the article that I initially linked to, a study was released (Link) that demonstrated sars-cov-2 infection of macrophages in vitro. As with Sars-cov, the infection was observed to be abortive, in that the virus did not successfully replicate upon infection. However, upregulation of pro-inflammatory chemicals was noted from the infected macrophages which suggests one possible mechanism for increased disease severity through ADE after vaccination.
The issue of immune enhancement seems to have been an obstacle to the development of a vaccine for Sars-cov, and both animal testing and in vitro experiments have suggested more severe disease when the infection was introduced in the presence of prior immunity, particularly neutralising antibodies to the spike protein. Given much of the Sars-cov-2 vaccine effort will expect to induce robust neutralising antibody response, this may be a cause for concern.
On the other hand, it is noted that in vitro experiments do not necessarily provide proof of ADE in vivo, and that certain ADE observations may be both virus and/or species-specific (Link). Further, challenge to sars-cov-2 vaccinated rhesus monkeys did not show signs of ADE. ADE can also be avoided through vaccine design, and various methods are described, including T cell vaccine (Link)
It is difficult to reach a firm conclusion on the matter, given the lack observable instance of ADE in sars-cov-2, but I find previous research hard to ignore and the absence of a sars-cov vaccine, whilst perhaps explained by substantially reduced need and funding, is telling. I think this is a critically important issue given how widespread vaccination is expected to be administered, and perhaps deserves more awareness.