It’s a two-shot vaccine, so what happens if people miss their second shot? Is a single shot still protective?
The Pfizer-BioNTech vaccine requires two injections, given 21 days apart, to prime the immune system well enough to fight off the coronavirus.

Two shots are needed, and the second shot is required to attain immunity. The gap between doses in the trial ranged between 19 and 42 days. Only 2 per cent of people in the trial missed their second dose so it isn’t entirely clear what happens under those circumstances.

Are there any side effects?
Sometimes, but they are mild. In the trial, the vaccine was generally well-tolerated, and an independent data monitoring committee reported no serious safety concerns.

The worst side effects were fatigue and headaches after the second dose. About 4 per cent of people reported fatigue and 2 per cent a headache.

Other side effects were pain at the injection site and muscle pain. These are “common reactions you would have with vaccination”,

Older adults reported fewer and milder side effects.

Does it work in older people?
Yes. Trial participants were aged up to 85, and the efficacy in people over 65 was 94 per cent – a tiny bit lower than the overall number but still very protective, and much higher than some vaccine experts feared. The vaccine hasn’t been tested in people aged over 85.

What about other vulnerable groups?
The vaccine appears to be equally effective regardless of recipients’ age, sex and ethnicity, according to BioNTech. It has been tested extensively in people who have already had the virus and doesn’t cause any ill effects. It has also been tested in people with “stable” pre-existing conditions – also known as comorbidities – including diabetes, cancer, hepatitis B, hepatitis C and well-managed HIV. Their response was as good as anyone else’s.

Does it protect everyone?
No. In the trials, out of about 20,000 people who were given the vaccine, eight caught covid-19 and one became seriously ill. In contrast, 164 people who received the placebo fell ill, nine severely. It isn’t known why some people didn’t respond to the vaccine. But a success rate of 95 per cent is about as good as it gets with any vaccine.

How much will it cost?

Unlike some of its rivals, BioNTech and Pfizer have not promised to supply the vaccine on a not-for-profit basis. In the US, the companies sold at least 100m doses to the government at $19.50 each, but the amounts paid by other countries — including the UK — have not been disclosed.

Source:

https://www.newscientist.com/article/2261805-everything-you-need-to-know-about-the-pfizer-biontech-covid-19-vaccine/#ixzz6g2CoHD7J

https://www.ft.com/content/74e41528-80c3-4b0f-b343-be43d90f0311

https://www.nytimes.com/interactive/2020/health/pfizer-biontech-covid-19-vaccine.html

https://www.pfizer.com/products