Extract all text between the same matching string from a given column

Shell Programming and Scripting
1

Hello All,
I have an input sample data like below (In actual I have many columns and few million rows).

Column1,Column2
4,2
1,5
Hello,4
1,4
Hello,2
3,5
Hello,8
4,5

Need the output (using awk and/or sed preferably) like below. Here I need all the lines between 2 matching strings(inclusive) from a particular column (in this case, column 1) but the matching strings are the same ones "Hello".
Also preserve the header too.

Column1,Column2
Hello,4
1,4
Hello,2
3,5
Hello,8

Thanks
Sidda

2

What operating system are you using?

What shell are you using?

How is the column to be searched specified?

From your given requirements, why isn't the output the same as the input? The "4" in column 1 on line 2 and the "4" in column 1 on line 9 appear to me to be identical strings; so why aren't they and all lines between them included in the output? Aren't the "4"s matching strings? Aren't the "4"s the same?

What have you tried to solve this problem?