problem changing spawnTime variable

I'm having trouble getting my objects to react accordingly. For testing, I have my timer set to spawn every second, then, when my score reaches 5 or above, I would like to change the timer to every 5 seconds.

As it is, the enemies still come every second. I have a Debug.Log() in there and it displays the spawnTime variable as 5, but the enemies still come every second.

I have a feeling it's because it is in my Start() function but in the update function, hundreds of enemies spawn. How can I get around this? Thanks

 using UnityEngine;
 using System.Collections;
 
 public class spawn : MonoBehaviour
 {
     // Prefab to spawn
     public GameObject spawnableObject;
 
     public GameObject[] prefab;
     private int timeToBegin = 2;
     private float spawnTime = 1;
     
     Vector3[] spawnPoints;
 
     int endOfArray;
 
     void Start()
     {
         //The point in which the new prefab will be spawned
         GameObject[] objs = GameObject.FindGameObjectsWithTag("SpawnPoints") as GameObject[] ;
         spawnPoints = new Vector3[objs.Length] ;
         
         for(int i = 0 ; i < objs.Length ; i++)
         {
             spawnPoints[i] = objs[i].transform.position ;
         }
         endOfArray = spawnPoints.Length;
         InvokeRepeating ("Spawn", timeToBegin, spawnTime);
     }
 
     void Update()
     {
         if(accelShotHS.score >= 5)
         {
             spawnTime = 5.0f;
             Debug.Log(spawnTime);
         }
     }
 }