Are vaccines the reason for the rapid drop in new cases?

I am a brain injured idiot with no relevant experience. I make observations and ask stupid questions.

This Tweet prompts a question I have wondered about:

The pandemic’s epicurve trajectory followed a similar path of past pandemics, when we did not have vaccines. The Spanish Flu of 1918, for example, was thought to have infected about 1/3d of the world’s population before it faded out.

We were told by “experts” that we need 70-85% vaccinated before we would get control. From my observing the trends and data, however, the reproduction rate began dropping, state by state, when estimated prevalence of those who had Covid-19 had reached about 30%. As immunity rose with vaccinations, cases plummeted. Above 50% (LA’s estimated prevalence of Covid-19 was 55%), cases plummeted.

While vaccines will close out the pandemic, it does seem the pandemic may have been starting to close out on its own – just as most past pandemics have done. Vaccines are always preferable – and safer – than having the actual disease.

Vaccines though do not explain what we have just seen in India – in a country of 1.4 billion people, vaccines played little role in this sudden drop off in cases.

Cases throughout the world are now plummeting – but 90% of the world is not yet vaccinated. If vaccines explain the drop in the U.S., what explains the drop in India and the entire world?

Similarly, all the way up until about 1-2 weeks ago, the “experts” told us “masks work” even as cases exploded in the US from late summer to early January.

Now that cases have gone down, we are told it is because of vaccines.

Really? Correlation is not causation. And when we look at all of the data there are many contradictions that go unexplained. Until a theory accounts for the contradictions, it is just a hypothesis and one that may not be true.

Related: Among all the hyperventilating over India the past few weeks, the media never, ever mentioned that the cases and deaths per population where just 1/4th that of the United States – when adjusted for population differences. India’s population is 4.26x larger than the U.S.