| Comment | An earth wire massively helps prevent electrocution. It does not prevent electrocution entirely.
A seatbelt massively helps prevent injury from car accidents. It does not prevent injury entirely.
Why do you still use earthed appliances and car seatbelts even though they don't entirely eliminate a risk? Because they massively reduce the risk.
Similarly, a vaccine does not prevent spread entirely. But it does massively reduce it. |
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