The vaccines may cause Vaccine-Enhanced Disease or Antibody-Dependent Enhancement

“COVID-19 vaccines designed to elicit neutralising antibodies may sensitise vaccine recipients to more severe disease than if they were not vaccinated.” 


“The specific and significant COVID-19 risk of ADE should have been and should be prominently and independently disclosed to research subjects currently in vaccine trials, as well as those being recruited for the trials and future patients after vaccine approval, in order to meet the medical ethics standard of patient comprehension for informed consent.”

Study: Informed consent disclosure to vaccine trial subjects of risk of COVID-19 vaccines worsening clinical disease 


“Their discussions included the need for data evaluating the theoretical risk for vaccine-induced disease enhancement, which is when vaccinated individuals who are subsequently infected with a virus develop disease that is worse than if they had not received a vaccine at all. Regulators acknowledged the urgency of proceeding to human clinical trials with SARS-CoV-2 candidate vaccines in light of the current COVID-19 pandemic, yet stressed the importance of preclinical and clinical risk mitigation strategies so that those enrolled in clinical trials are not exposed to unreasonable risk. “

FDA and EMA Collaborate to Facilitate SARS-CoV-2 Vaccine Development

Pfizer recognized the possibility of vaccine enhanced disease in this trial:

“During the phase 2/3 portion of the study, a stopping rule for the theoretical concern of vaccine-enhanced disease was to be triggered if the one-sided probability of observing the same or a more unfavorable adverse severe case split (a split with a greater proportion of severe cases in vaccine recipients) was 5% or less, given the same true incidence for vaccine and placebo recipients. Alert criteria were to be triggered if this probability was less than 11%.”

Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine

“Our results indicate that mutations present in the spike protein of the Lambda variant of interest confer increased infectivity and immune escape from neutralizing antibodies elicited by CoronaVac. These data reinforce the idea that massive vaccination campaigns in countries with high SARS-CoV-2 circulation must be accompanied by strict genomic surveillance allowing the identification of new isolates carrying spike mutations and immunology studies aimed to determine the impact of these mutations in immune escape and vaccines breakthrough.”

Study: Infectivity and immune escape of the new SARS-CoV-2 variant of interest Lambda

“Vaccine-enhanced disease (VED) is a type of adverse event in which disease severity is increased when a person who has received the vaccine is later infected with the relevant pathogen. VED can occur during research with experimental vaccines and/or after vaccine licensure, sometimes months or years after a person receives a vaccine.”

Study: Vaccine-enhanced disease: case studies and ethical implications for research and public health

“In conclusion, ADE may occur in people receiving vaccines based on the original Wuhan strain spike sequence (either mRNA or viral vectors) and then exposed to a Delta variant.”

Study: Infection-enhancing anti-SARS-CoV-2 antibodies recognize both the original Wuhan/D614G strain and Delta variants. A potential risk for mass vaccination?

ADE occurs when the antibodies generated during an immune response recognize and bind to a pathogen, but they are unable to prevent infection. Instead, these antibodies act as a “Trojan horse,” allowing the pathogen to get into cells and exacerbate the immune response.

Antibody-dependent Enhancement (ADE) and Vaccines

As of October 2020, this was the FDA’s working list of possible adverse events. The people getting the shots did not get this information (informed consent).

You can see all of the slides here.