Autumn Horse It’s The Most Wonderful Time Of The Year Shirt

The idea was to make it easier to keep study blinded to the subjects. Vaccines usually cause some injection site pain or localized muscle soreness but a saline placebo wouldn't, so you know you aren't in the placebo group if there's some minor soreness at the injection site. Using meningitis vaccine is supposed to avoid that, although I believe some other vaccine trials are just using saline. Its a double blind study so to make it easier to keep people in the dark about whether they got the new vaccine they give them a real one that has well studied effects.

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