A cheap and easy inactivated vaccine for COVID-19
Suppose a person with COVID-19 coughs into a bag. Let the bag sit in the sun for, say, 72 hours -- so as to make the virus inactive.
Could a healthy person breathe in the inactivated virus from the bag (perhaps done multiple times) to (eventually) trigger an antibody response to the virus?
Is this a known way to make inactivated vaccines? Has it been studied, perhaps for other viruses?
Are there known reasons why this would not work?
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It wouldn't be consistent. (as some of the commenters pointed out).
Here are some numbers:
The concentration of virus in sputum can vary by a factor of 10^5.
(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7224694/ for count of RNA in sputum)
Best guess is that 100-1000 RNA copies is a "quanta" in the Wills-Riley Model (http://tinyurl.com/covid-estimator)
If it's known how many RNA copies is good to generate immune response but not disease, it's very hard to get the right level.
There will be variation in immune response / disease contracting.
But, this doesn't rule it out as possible. In fact, nothing can prove it's impossible except running every variation of what you're saying. To prove it's possible, you would need to run the controlled experiment.
But that experiment would be considered unethical.
You could try it in rats or mice first. But there is no good animal model for COVID19 right now (from what I read).
The only approved inhaled vaccine is the flu vaccine delivered intra-nasally. It uses a live attenuated virus. There are a whole list of people who should not receive it because it's a live virus, and it works better for children, but only is 40% effective for adults.
The main issue is
The intranasal LAIV, recommended for children above the age of 2 years, induces a broader immune response wherein protection is not antibody mediated and probably involves undefined multiple correlates of protection.
and that's with a live virus.
How well would a dead inhaled virus work? Well, we have some data from MERS that suggests that vaccination with whole dead virus can increase lung pathology when exposed to live virus.
The implication of the current study is that application of an inactivated MERS-CoV vaccine for prevention of MERS in humans may carry a risk for lung immunopathology if subsequently exposed to MERS-CoV. The study also leads us to suggest that the extensive background of preclinical experience with inactivated SARS-CoV vaccines may be applicable to inactivated MERS-CoV vaccines.
So, your cheap vaccine may increase your risk of death or disease when exposed to the live virus.
Influenza Vaccination Strategies: Comparing Inactivated and Live Attenuated Influenza Vaccines www.cdc.gov/flu/prevent/nasalspray.htm
Immunization with inactivated Middle East Respiratory Syndrome coronavirus vaccine leads to lung immunopathology on challenge with live virus www.ncbi.nlm.nih.gov/pmc/articles/PMC5027702/
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