You should recognize that while yellow fever vaccination provides complete lifetime protection, if you get yellow fever, as it is a viral disease, there are not a lot of treatment options but your doctor could witness your signature on your last will and testament. There are a lot of other travel vaccinations such as hepatitis, typhoid and tetanus that you also need to consider.

You don't get a vaccination against malaria, you take pills, either daily or weekly, depending on what sort you take.
First, you need to talk to your doctor or a travel clinic about which ones will be best for you.

You do need protection against malaria, have a look at this malaria map

Do you mean the destination or just traveling with a 4 week old baby? If it's your first child and you haven't had it yet, then you might want to leave the decision until a bit later, when you decide whether you still have the energy and enthusiasm (and to ensure everything is going OK). We found it fairly daunting traveling with our first son at around the same age (and just locally). But - if you are feeling confident and relaxed then it is could be a fairly easy age to travel with (especially if you are breastfeeding). You would need to think about vaccinations and when they are due and what the baby might be missing. China itself should be fine with a baby, but there is a high density of people which increases your likelihood of coming into contact with things.

First off, good for you, the world is a wonderful place to discover, and explore. It is amazing how each culture is different, the people so different in one country, and food changes so much regionally. Top it all off with history, which every country has a story worth reading about. especially in EU.

That said, I agree with others to look into a few nice shorter trips, to areas backpackers have been going to for decades and its easy to conquer, relatively safe.

Since you are in New Zealand, consider SE Asia as a start, and get a cheap flight to Bangkok Thailand or Singapore etc, and start there for a few weeks. These cultures are alos exotic and the landscapes nearby fun to enjoy and explore.

Your Passport will get you into most countries backpackers go to, with a Tourist Visa on Arrival, meaning Immigration at the airport, border or port, will automatically give you permission to visit for a set period, 30 days, 60 days, 90 days, and some even 6 months.

for a USA Passport, Most of Asia, (except China/Myanmar/Vietnam) you can travel Visa free, as well as North America (Canada/MX) and most of EU, all of Central America (Guatemala to Panama) and most of South America, (90% of Latin America)and parts of Africa/Middle East/Persia.

I would think language wise, Spanish would be easiest and best for EU, and all of Latin America. Asia the dialects are all so different and also hard to master the language due to vowel tones, English will get you by overall.

Africa/Middle East a combination of English and French is good, as many Arabic countries were once occupied/aligned by the French or the British.

You will also need to start collecting your Jabs (Health Vaccines) and keep your Health Card updated to enter many countries, do to Yellow Fever, Typhoid and Tetanus. Hep-A & B is also a must, especially B when sexually active, regardless of country.

USA is best to see the highlights of the national parks via a rental car, so you need to be over 25 and have a decent budget to rent cars. Not a big backpacker culture, its mainly a car society, overland public transport is limited overall.

There are also workaday programs where you can work for free rom and board as well, in may countries, from Organic Farms to with endangered species to wine bars and cafes. This is a great way to spend time in a culture on a budget. You also have WOOFing.

Happy Trails.

Tim

I don't think you have understood the question. The vaccine was never obtained in Tanzania, it was administered in Ethiopia.

It could be a problem,

Not really because if not life-time then 10 years and the vaccination was done only 1 year ago.

Yes. The vaccination has always been good for 10 years and I believe now it's for life as a booster is no longer necessary.

In Southeast Asia, the issue is not going to be so much "cheap" as "available" and "reliable."

The one country I would suggest is Thailand. Immunization is generally subsidized by the government, so vaccine prices are cheaper. There is excellent health care available in Bangkok, including immunization against rabies.

The Thai Travel Clinic charges 373 Baht (US$11) per rabies shot. The Queen Saovabha Memorial Institute (also known as the Thai Red Cross or the Snake Farm) in Bangkok is the leading rabies clinic in Bangkok. You can also get pre-exposure immunization from the Travel Clinic at Bumrungrad Hospital and other reputable clinics. Prices will be about the same.

Don't forget that immunization is a series of three shots over the course of a month, so you will need to hang around (or be able to return to) Bangkok for that long.