About a week after Carnival Cruise Line announced it would drop its vaccine requirement for many sailings next month, Denise Jewell shared information about a Mother's Day cruise she is organizing with her women's travel Facebook Group. Bookings that previously may have taken days or weeks to come through, Jewell said, took just hours.

Jewell, a travel specialist and owner of Opulence Travel Agency, said there is a large number of unvaccinated travelers who could not board ships before. Carnival currently requires unvaccinated travelers 5 and older to obtain an exemption "limited to a small number of guests," according to its website, but will nix that requirement for many voyages in September.

"Now, demand is definitely going to go up because now they can travel on a cruise," she said.

Other major cruise lines including Princess Cruises, Royal Caribbean International and Holland America Line also said they would welcome all passengers regardless of vaccination status on many voyages, and roll back testing rules for vaccinated passengers. Here is how those changes – and the resulting demand – might impact your travel plans.

How much have cruise bookings gone up?

Some major cruise lines have seen spikes in booking activity after announcing the rule changes. Carnival, for instance, said last week that those numbers on Aug. 15 were almost double the equivalent day in 2019, days after the line announced changes to its protocols.

Starting Sept. 6, the line will no longer require unvaccinated travelers to obtain an exemption for sailings less than 16 nights, and vaccinated passengers will not have to take a COVID test before those trips, with some exceptions.

"We have previously disclosed strong occupancy projections for the summer, and our bookings through the end of 2022 have also been very solid," Christine Duffy, the line's president, said in a news release. "With the further alignment of protocols to other vacation choices, our guests are booking the remaining 2022 inventory, and getting a head start planning for 2023. Mid-August is typically not a busy month for cruise bookings, but it’s clear that pent-up demand for Carnival has not been satisfied and guests are responding very favorably to our updated protocols."

Norwegian Cruise Line Holdings Ltd. saw a similarly positive response after the company said it would drop pre-cruise testing for vaccinated travelers and welcome all unvaccinated passengers aboard. President and CEO Frank Del Rio said during an Aug. 9 earnings call that following the announcement, the cruise line operator saw "one of our top three best booking days of the year."

The Centers for Disease Control and Prevention continues to recommend travelers be up to date with their COVID-19 vaccines before traveling, and that they get tested before and after their cruise.

What does the increased demand mean for travelers?

Drew Daly, senior vice president and general manager of travel agency franchise Dream Vacations, said as soon as travelers know they want to take a cruise "they need to take action because prices are going to go up" as inventory is reduced.

Given that there are "only so many cabins on a ship to begin with and there and only so many ships," he said capacity and inventory will become more scarce, particularly when it comes to holiday travel or spring break next year. Dream Vacations has seen an increase in bookings in response to the rule changes, Daly said, though he did not have exact numbers available.

Jewell also noted that ships may be more crowded, which could change the on-board experience, leading to longer lines for food, for instance.

Historically, travelers have generally booked cruises six to nine months out, Daly said. During the pandemic, those windows shrank, but he expects them to increase again. He recommended working with a travel advisor who can walk you through the process, and may have access to promotional offers or special amenities.

Jewell also recommended guests book further in advance. She advises travelers to book three to 10 months in advance under normal circumstances, depending on whether they are using a payment plan, but would now suggest booking a year ahead "because it's just going to book up a lot faster."

Travelers looking to book a last-minute trip are not out of luck, though. There are more than 130 cruises under $1,000 departing between Sept. 6 and 13, according to Cruise Sheet, which aggregates cheap fares. Those prices include taxes and port fees.