Good idea to deliver pertussis vaccine nasally. The live attenuated strain of Bordetella pertussis, BPZE1 was developed as a live nasal pertussis vaccine candidate, and currently its in clinical trial in human! You are correct: the side effects may be minimized, and efficacy of vaccination may be improve, because mucosal vaccination can target antibody responses and T cells at mucosal surface, and also in systemic circulation as well.

Check out the mesh nebulizer(s) by Aerogen - known to be highly non-destructive to whatever is being nebulized...

I would be worried about using this route as you run the risk of causing lung inflammation and pathology , although it seems more natural and you would get an immune response it is more likely to have serious consequences for the local tissue than a conventional subdermal or intramuscular injection

Vaccination is always a balance between the side effects and immunogenicity. We should try to minimize the risk of causing lung inflammation and pathology, and there are a lot of potential strategies to minimize such risk. Also there are some risks for a conventional vaccination routes as well.

Sarah Howie

Oral polio is being administered by ingestion with very rare side effect when it reverts . MMR are also live attenuated vaccine, why it should cause lung inflammation or pathology when inhaled.

Aerosol-mediated delivery is certainly more and more in focus with the potential for high levels of dosing, non-invasive adminstration and the potential for long term protection from pulmonary mucosal exposure.

The WHO-led study on inhaled measels vaccine was published last year, and whilst aerosol-mediated delivery was not as effective as injection in this study......it provides sufficient rationale for further human studies. 

https://www.researchgate.net/publication/275033879_A_Randomized_Controlled_Trial_of_an_Aerosolized_Vaccine_against_Measles

The limitation in aerosol-mediated delivery is the ability to deliver a sufficient dose, reliably and reproducibly within a given patient population, and so aerosol generator selection is critical.

 [https://www.researchgate.net/publication/258041169_The_Science_Guiding_Selection_of_an_Aerosol_Delivery_Device]

Factors such as patient breathing parameters, patient interface (mouthpiece/facemask) droplet size, emitted dose, residual volume (i.e. drug never available to the patient), post-aerosolisation activity and lung dose all combine to dictate the eventual efficacy of an aerosolised vaccine.

These are factors that are not typically well controlled/understood and should an inappropriate aerosol delivery system be used, sub-optimal results shall likely follow.

Colleagues and I recently published on aerosol delivery systems for NHP to demonstrate that 1) breathing patterns and 2) device selection have a significant effect on the inhaled dose. Same rules apply to humans.

https://www.researchgate.net/publication/286445626_Optimization_and_Dose_Estimation_of_Aerosol_Delivery_to_Non-Human_Primates

Regarding potential side effects.............some points of note here:

1) existing e.g oral formulations may well need to be reformulated for pulmonary delivery. Excipient choice will have a large influence on side effects.

2) typically....but not always.....topical administration to the lung surface provides and direct and more immediate response. As such the minimum effective dose may be different/lower. Take the example of inhaled antibiotics used to treat lung infection. 

3) regarding lung inflammation etc........again the root cause of inflammation will either be the vaccine itself (and so would illicit a response regardless of route of administration) or the excipients, which I propose would need to be selected for pulmonary targeting in any case.

Article The Science Guiding Selection of an Aerosol Delivery Device

Article A Randomized, Controlled Trial of an Aerosolized Vaccine aga...

Article Optimization and Dose Estimation of Aerosol Delivery to Non-...