Question

Inactivated vaccine primarily relies on proteins to elicit immune responses. My question is, does inactivated COVID vaccine also contain mRNA that could beactivelytranscribed into new proteins in human body, similar to those mRNA vaccine? To my knowledge, the mRNA in mRNA vaccine is slightly modified such that it can be transcribed. Without those modifications, can mRNA in inactivated vaccines still be transcribed? If the answer is yes, then, is the concentration of active mRNA high enough that the transcription activities can be detected? Short answer: no. Basically all the inactivated vaccines use cross-linking agents that will cross-link or damage the RNA (e.g.aldehydes,Beta-propriolactone or ethylene imine) through a chemical reaction. Many of these sorts of vaccines are then formed into subunit vaccines which undergo extensive purification to get the antigenic protein of interest. A reasonable reference for this is (also the second link above): Iris Delrue, Dieter Verzele, Annemieke Madder & Hans J Nauwynck (2012) Inactivated virus vaccines from chemistry to prophylaxis: merits, risks and challenges, Expert Review of Vaccines, 11:6, 695-719, DOI:

Answer 1

Inactivated COVID-19 vaccines do not contain transcribable mRNA like mRNA vaccines do. Instead, they include killed or inactive pathogens or their key antigens to induce an immune response. The inactivation process, which can involve chemicals like formalin, generally damages any RNA preventing transcription.

Step-by-step explanation:

Inactivated COVID Vaccines and mRNA

Inactivated vaccines, such as some COVID-19 vaccines, do not contain mRNA that can be actively transcribed into proteins in the human body. Unlike mRNA vaccines like those made by Pfizer and Moderna, which use modified nucleotides to ensure stability and efficient translation into proteins, inactivated vaccines utilize killed or inactive pathogens. These vaccines are often produced through subunit vaccine strategies, isolating only the essential antigens of a pathogen to induce an immune response without the risk of causing active infection.

In the case of production, the pathogen is typically grown in culture, then inactivated with agents such as formalin, beta-propinolactone, or an imine. This process ensures that the vaccine cannot reproduce or cause disease, but still elicits a strong immune response. Furthermore, the inactivation methods used would typically damage any genetic material, such as RNA, preventing it from being transcribed. Consequently, inactivated vaccines primarily trigger a response based on the presence of viral proteins rather than any nucleic acid-based mechanism.

Additionally, some inactivated vaccines may require higher doses or multiple boosters as the immune response they generate is generally weaker and less comprehensive compared to live attenuated vaccines. In general, these vaccines provide an essential public health benefit by preventing viral infections and their spread, significantly reducing morbidity and mortality due to diseases such as polio, measles, and now COVID-19.