I take it every year since I've been diagnosed with a heart condition. There is a new one every year because it is an RNA (retro) virus. RNA viruses can mutate when they replicate, creating new strains. Every year the flu vaccine is effective for 3-5 different strains.
Covid is an RNA virus. Since folks didn't, couldn't or wouldn't lock down, wear masks and social distance when all this started, it has mutated. It will continue to mutate because folks are STILL refusing to do these things or get vaccinated.
Retrovirus vs. DNA Virus
A DNA virus is a virus in which the genetic information is stored in the form of DNA (deoxyribonucleic acid). It replicates using a DNA-dependent DNA polymerase. The nucleic acid is usually double-stranded DNA (dsDNA) but may also be single-stranded DNA (ssDNA). Examples of DNA viruses are the herpes simplex virus and the poxvirus.
Retroviruses use their RNA and a special enzyme called reverse transcriptase to create DNA, which then specifies RNA, which in turn creates proteins. The retrovirus then integrates its viral DNA into the DNA of the host cell, which enables replication of the retrovirus.
The extra step makes retroviruses more prone to mutation than most viruses, causes them to evolve more quickly than other viruses. This process makes the HIV retrovirus, the best-known human retroviral disease that causes AIDS, very resistant to treatment.
In humans and many other complex organisms, DNA stores hereditary information in genes. However, different types of viruses use several different nucleic acids in their genetic material. As a result, genetic information can be stored in RNA or DNA. For example, retroviruses only have RNA. The...
sciencing.com