The primary purpose of an Initialization Vector (IV) in encryption is to ensure that the same plaintext encrypted with the same encryption key will produce different ciphertext each time it is encrypted. This variability is crucial for securing repetitive data patterns and preventing certain types of cryptographic attacks, such as replay or pattern analysis attacks. The IV adds randomness to the encryption process, making it more secure by ensuring that encrypted messages are unique, even if the plaintext and key remain unchanged. This prevents attackers from deducing patterns or inferring any useful information from repeated ciphertext.