How widespread was the immunization for swine flu in 1976?

I have a little running bet with my husband that the older generations (mine) in the US received some kind of immunity from previous infection - either by exposure or inoculation, but can't find anything on the Web about the program they used in 1976 for the shot they developed -

There is a similarity between the swine flu epidemic centered in Mexico City and the Spanish influenza epidemic of 1918-19. Infants and elderly were spared. It was the young adults with robust immune systems that were the prime victims and the disease took them literally by storm. What happens with young and healthy patients is that their immune systems react so strongly that they can triggers something known as a "cytokine storm".

In response to every infection, the body has a number of ways to fight back against the invading enemy. Cytokines are part of this defense. The name "cytokine storm" basically describes an over-reaction of a healthy immune system that has over-reacted and is damaging the body, causing failure of multiple organ systems. It can be triggered by many things, including viruses, although it's not common for human influenza A virus strains to cause it. The same thing occurs with new swine flu virus and the body has no defenses built up. When infected the body's own defensive systems are triggered to a powerful extent and cause havoc to the immune system. It鈥檚 something like dropping an H-bomb on a suspected burglar in your back yard. The result is to kill, or needlessly harm, the patient

In children the immune responses are still developing, while the elderly immune function tends to be weaker due to the aging process. Both groups have weak immune system that is why they are vulnerable to complications from the regular flu and tend to get pneumonia and other opportunistic infections after being weakened further by the regular flu. Fortunately, they don't have systems that react strongly to the flu itself that can generate the cytokine storm. However, the healthy approximately 15 to 60 year old individual the most likely to actually succumb to the swine flu.

A cytokine storm can overcome the nervous system and cause breathing and internal organs problems, which is why hospitals put critical flu patients on assisted machines. What really frightens experts in the pandemic field is the fact that most hospitals only have a few of these facilities and they are often in use for surgical or other critical patients. There is simply no way to provide interim support for tens of thousands of pandemic flu victims, even in advanced countries with a strong hospital system. The equipment just doesn't exist to put them all on breathing machines until their bodies are able to recover naturally.

http://www.capitalcentury.com/1976.html